Routing TCP/IP Vol 1 Notes

[tranmyphuc]

Chào các bạn !!!!
Những ai đã và đang học về mạng máy tính hẵn sẽ biết về 2 cuốn sách kinh điển nổi tiếng Routing TCP/IP . Cuốn sách bao hàm những kiến thức từ cơ bản đến nâng cao về mạng máy tính. Tuy nhiên, những bài viết sau đây sẽ giúp bạn có cái nhìn khái quát hơn và dễ dàng ghi nhớ cũng như tiếp cận nhanh hơn với Routing TCP/IP . Hi vọng những Notes này sẽ hỗ trợ một phần nào đó cho bạn trong con đường chinh phục đỉnh tháp cisco.

Chúc các bạn vui !!!

* Chapter 1: TCP/IP Review
* Chapter 2: IPv6 Overview
* Chapter 3: Static Routing
* Chapter 4: Dynamic Routing Protocols
* Chapter 5: Routing Information Protocol (RIP)
* Chapter 6: RIPv2, RIPng, and Classless Routing
* Chapter 7: Enhanced Interior Gateway Routing Protocol (EIGRP)

Chapter 1: TCP/IP Review

Internet Protocol (IPv4)

• Version (4 bits) - IP version (4 or 6)
• Header lentgh (4 bits) - Length of header plus any options
• Type of Service (TOS) (8 bits) - Used for QoS; can also be evaluated as DiffServ Code Point (DSCP)
• Total length (16 bits) - Total packet size
• Identifier (16 bits) - Identifies fragments belonging to a single original packet
• Fragmentations flags (3 bits) - Three flags: unused, Don't Fragment (DF), and More Fragments (MF)
• Fragment offset (13 bits) - Specifies the offset of a fragment from the beginning of the original packet (in units of eight bytes)
• Time To Live (TTL) (8 bits) - Tracks hop count
• Protocol (8 bits) - Identifies the upper-layer protocol
• Header checksum (16 bits) - Used for header error detection
• Source address (32 bits)
• Destination address (32 bits)
• Options (variable length) - Optional attributes generated by the originator

Common IP options:

• Loose source routing - A list of IP addresses (router interfaces) the packet should traverse
• Strict source routing - A routing path which must be followed exactly
• Record route - Routers traversed record the address of their outbound interface on the packet
• Timestamp - Like record route but also includes a timestamp

Address Resolution Protocol (ARP)

ARP header:

• Hardware type (16 bits) - Identifies the type of layer 2 technology (Ethernet, HDLC, etc)
• Protocol type (16 bits) - Identifies the network-layer protocol
• Hardware address length (8 bits) - Length of the data link address in bytes (e.g. MAC = 6)
• Protocol address length (8 bits) - Length of the network address in bytes (e.g. IP = 4)
• Operation (16 bits) - Packet type (request/reply type)
• Sender's hardware address
• Sender's network address
• Target hardware address
• Target network address

Cisco routers cache ARP entries for four hours by default (this can be modified with arp timeout <seconds> at interface configuration).
Proxy ARP

Proxy arp allows a router to issue ARP replies to one subnet on behalf of a host in another subnet, to facilitate inter-subnet communication with a host not configured with a default gateway.
The proxy ARP reply will contain the router's own hardware address for that subnet.
Gratuitous ARP

A gratuitous ARP request is one requesting a reply for the sender's own IP address.
Gratuitous ARP can be used to check for duplicate addresses or announce the existence of a new host.
Reverse ARP (RARP)

Reverse ARP occurs when the sender requests the network address for a given hardware address.
For purposes of initial device addressing, RARP has been superseded by BOOTP and DHCP.
Internet Control Message Protocol (ICMP)

ICMP header:

• Type (8 bits)
• Code (8 bits)
• Checksum (16 bits)
• Other fields... (variable)

Common ICMP types:

• 0 - Echo reply
• 3 - Destination unreachable
• 5 - Redirect
• 6 - Alternate host address
• 8 - Echo
• 9 - Router advertisement
• 10 - Router selection
• 11 - Time exceeded
• 12 - Parameter problem
• 13 - Timestamp
• 14 - Timestamp reply
• 30 - Traceroute

Transmission Control Protocol (TCP)

TCP header:

• Source port (16 bits)
• Destination port (16 bits)
• Sequence number (32 bits) - Identifies the position of a segment within a stream
• Acknowledgment number (32 bits) - Identifies the sequence number the source next expects to receive
• Header length (4 bits)
• Reserved (4 bits)
• Flags (8 bits)
• Window size (16 bits) - Flow control; specifies the amount of data that may be transmitted from the peer between acknowledgments
• Checksum (16 bits) - Error detection for the header and payload
• Urgent pointer (16 bits) - Points to the end of urgent data; used only when the URG flag is set
• Options (variable)

TCP flags:

• CWR - Congestion window reduced
• ECE - ECN-Echo
• URG - Urgent data
• ACK - Acknowledgment
• PSH - Push
• RST - Reset
• SYN - Synchronize
• FIN - Final

User Datagram Protocol (UDP)

UDP header:

• Source port (16 bits)
• Destination port (16 bits)
• Length (16 bits)
• Checksum (16 bits

[tranmyphuc]

Chapter 2: IPv6 Overview

IPv6 Addressing

IPv6 addresses are presented in 16-bit hexadecimal groups separated by colons. For example, 3ffe:1944:0100:000a:0000:00bc:2500:0d0b.
Shorthand rules:

• One group of all-zero segments can be presented with a double-colon (::)
• Leading zeros in each segment may be omitted

Subnet identification is performed in CIDR (bit count) notation (/64).
::/0 indicates an all-zeros or wildcard address.
::/128 represents an unspecified address.
Address Types

IPv6 addresses can be one of three types: unicast, anycast, or multicast.
Broadcast functionality is provided by the "all-nodes" multicast address.
Address types are identified by their leading bits:
BinaryHexType 11111111FF00::/8Multicast 11111110 10FE80::/10Link-local unicast 11111110 11FEC0::/10Site-local unicast (deprecated) 0012000::/3Global unicast (currently allocated) Global Unicast

A global unicast address is broken into three sections:

• Global routing prefix (48 bits)
• Subnet ID (16 bits)
• Interface ID (64 bits)

Local Unicast

Link-local unicasts are unique only to a single layer 2 link.
Site-local unicasts were defined in the original IPv6 standard bit have been replaced by Unique Local Addresses (FC00::/7) in RFC 4193.
Anycast

An anycast address is one address configured on multiple end nodes; dynamic routing will ideally forward traffic to the "nearest" or least-cost anycast server.
Any global unicast applied to more than one device can be considered any anycast address.
Multicast

A multicast address identifies a logical group of devices.
Multicast address structure:

• Multicast prefix (8 bits) - Always 0xFF
• Flags (4 bits)
• Scope (4 bits)
• Group ID (112 bits)

Address Scopes:

• 0x0 - Reserved
• 0x1 - Node-local
• 0x2 - Link-local
• 0x5 - Site-local
• 0x8 - Org-local
• 0xE - Global
• 0xF - Reserved

Embedded IPv4 Addresses

Different transition technologies have different ways of embedding an IPv4 address in an IPv6 address. Some examples for 10.23.1.5 are:

• FE80::5EFE:10.23.1.5 (ISATAP)
• ::FFFF:10.23.1.5 (SIIT)
• FEC0:0:0:1::10.23.1.5 (TRT)
• 2002:0A17:0105::/48 (6to4)

IPv6 Header

IPv6 headers have a fixed 40-byte length.
Header format:

• Version (4 bits) - Always set to 6
• Traffic class (8 bits) - DiffServ Code Point (DSCP)
• Flow label (20 bits) - An arbitrary field for differentiating traffic flows
• Payload length (16 bits) - Indicates the length of the payload (header length is not included)
• Next header (8 bits) - Identifies the extension header or upper-layer protocol that follows
• Hop limit (8 bits) - Decrementing hop counter (TTL)
• Source address (128 bits)
• Destination address (128 bits)

Extension Headers

Extensions headers provide for optional extended capabilities such as hop-by-hop options and IPsec encryption.
Next header values:

• 0 - Hop-by-hop options
• 43 - Routing
• 44 - Fragment
• 50 - ESP
• 51 - AH
• 59 - No next header
• 60 - Destination options

If a header is the last in the stack, its next header field will identify the upper-layer protocol that follows (e.g. 6 for TCP or 17 for UDP).
RFC 1883 specifies the order in which extensions headers should appear if they are used.
ICMPv6

IPv6 implements its own version of ICMP, defined in RFC 2463.
Like ICMPv4, ICMPv6 uses type/code pairings to identify field types.
Common field types:

• 1 - Destination unreachable
• 2 - Packet too big
• 3 - Time exceeded
• 4 - Parameter problem
• 128 - Echo request
• 129 - Echo reply
• 130 - Group membership query
• 131 - Group membership report
• 132 - Group membership reduction

Neighbor Discovery Protocol (NDP)

NFP is defined in RFC 2461
NDP functions:

• Router discovery
• Prefix discovery
• Parameter discovery - Link MTU, etc.
• Address autoconfiguration - Replaces DHCP
• Address resolution - Replaces ARP
• Next-hop determination - Link-layer address for next hop
• Neighbor unreachability detection
• Duplicate address detection
• Redirect - A router can inform a host of a better path out of the link

NDP uses ICMPv6 to exchange messages.
NDP messages types:

• Router Solicitation (RS) (Type 133) - Sent by hosts to request an RA
• Router Advertisement (RA) (Type 134) - Originated by routers to announce their existence
• Neighbor Solicitation (NS) (Type 135) - Facilitates link-layer address resolution and duplicate address detection
• Neighbor Advertisement (NA) (Type 136) - Response to an NS
• Redirect (Type 137) - Used by a router to inform a host of a better path out of the link

Address Autoconfiguration

On broadcast links, the interface ID (the second half of an IPv6 address) can be automatically generated by converting a 48-bit MAC address to a 64-bit EUI-64 address.
MAC-to-EUI64 conversion:

1. 0xFFFE is inserted between the two 24-bit halves of the MAC
2. The Universal/Local bit (7th bit) is flipped from 0 to 1

For example, 0000:0A0B:1234 becomes 0200:0AFF:FE0B:1234.
An EUI-64 identifier can be joined with a link-local prefix (FE80::/10) to form a complete link-local address.
A host can receive a global IPv6 address using either stateful or stateles autoconfiguration.
Stateful autoconfiguration uses DHCPv6 to request an IPv6 address from a server.
In stateless autoconfiguration, a host simply adds its interface ID to a prefix received in a router advertisement (RA).
Duplicate Address Detection (DAD)

DAD is performed on initial configuration of all addresses except anycasts.
New addresses are marked as tentative and cannot be used until they have been verified.
Neighbor Address Resolution

Layer 2 information for IPv6 neighbors is stored in the neighbor cache (similar to the ARP cache for IPv4).
Privacy Addresses

RFC 3041 defines IPv6 privacy addresses to alleviate privacy concerns over using a static, globally unique identifier (MAC address) as the interface ID.
Privacy addresses use a randomly-generated interface ID, which changes on a regular basis and/or when a new prefix is received.

[tranmyphuc]

Chapter 3: Static Routing

A routing table can be populated in three ways:

• Subnets gleaned from directly connected networks
• Manual configuration (static routes)
• Automatically via one or more dynamic routing protocols

A route's next hop must be reachable for the route to take effect.
Configuring Static Routes

IPv4:

Router(config)# ip route <destination> <mask> [<interface>] [<next hop>]
Router(config)# ip route 172.16.0.0 255.255.0.0 192.168.1.1
Router(config)# ip route 10.0.0.0 255.0.0.0 Serial0/0 192.168.2.2

Specifying only an outbound interface rather than a next-hop address assumes that the destination network is directly connected to that interface.
IPv6:

Router(config)# ipv6 route <destination>/<masklen> [<interface>] [<next hop>]
Router(config)# ipv6 route fec0::8:0:0:0:0/64 fec0::1:204:c1ff:fe50:f1c0
Router(config)# ipv6 route fec0::4:0:0:0:0/64 Serial0/0 fec0::2:2b0:ca4ff:fe73:459

IPv6 requires the next-hop address to be specified when configuring a route destined out a broadcast (Ethernet) interface.
Advanced Static Routing

Floating Static Routes

A floating static route is one configured with a higher administrative distance. It will only be used if more preferable routes for a destination fail.
Load Sharing

Multiple static routes can be configured to support equal-cost load sharing.
By default, Cisco Express Forwarding (CEF) performs load balancing per source-destination pair; all packets from one source to one destination will traverse one interface.
CEF also supports per-packet load balancing for IPv4 traffic.
The CEF load-balancing method can be adjusted:

Router(config)# ip load-sharing {per-destination | per-packet}

Recursive Lookups

A recursive lookup occurs when a route points to network not directly connected; one or more subsequent lookups are required to determine the next hop.
Troubleshooting Static Routes

Remember to verify both directions of traffic flow when tracing a path.
When a router or interface hardware is replaced, a new EUI-64 identifier will be used; this may require redefining a static route.

[tranmyphuc]

Chapter 4: Dynamic Routing Protocols

Distance Vector Routing Protocols

The term distance vector is derived from a list (vector) of distances and directions to destinations.
Distance vector protocols include:

• Routing Information Protocol (RIP)
• Xerox Networking System (XNS) RIP
• Novell IPX RIP
• Cisco Interior Gateway Routing Protocol (IGRP)
• Cisco Enhanced IGRP (EIGRP)
• DEC DNA Phase IV
• Appletalk Routing Table Maintenance Protocol (RTMP)

Common distance vector characteristics:

• Periodic updates
• Reliance on neigbhors to propagate advertisements
• Broadcast updates
• Full routing table updates (advertising the entire table every time)

The per-hop nature of distance vector advertisements is known as routing by rumor.
Route invalidation timers control how long a route will remain in the routing table without being confirmed by a neighbor.
Split horizon prevents routing loops by preventing the readvertisement of a route to the neighbor from which it was learned. Router A will not advertise routes learned from router B back to router B.
Poison reverse extends the concept of spit horizon by readvertising a learned route back to the neighbor with an infinite metric. Router A will advertise routes learned from router B back to router B with an infinite metric, ensuring router B knows said routes are not reachable via router A.
Holddown timers place a restriction on how often a route may be updated in the table.
Link State Routing Protocols

Link state routers all share the same complete view of the network.
Link state protocol include:

• Open Shortest Path First (OSPF)
• ISO Intermediate System to Intermediate System (IS-IS)
• DEC DNA Phase V
• Novell NetWare Link Services Protocol (NLSP)

Neighbors synchronize their databases upon forming an adjacency. Hello packets are used to form and maintain adjacencies.
Link state protocols converge faster than distance vector protocols because routes can flooded to neighbors without having to run the routing algorithm.
Sequence numbers are used to identify the revision of an advertisement.
Advertisements are aged and will eventually expire from the database if they are not refreshed periodically.
Networks are commonly divided into link state areas to reduce demand on CPU, memory, and bandwidth required to maintain the database.
Interior and Exterior Gateway Protocols

An autonomous system (AS) is a logical network under a common administration.
Interior Gateway Protocols (IGPs) run within an autonomous system, while Exterior Gateway Protocols (EGPs) run between autonomous systems.

[blueman]

Chào bạn,

Bài này của bạn rất hay vì Subnet là một vấn đề mà chúng tav(networker) cần phải biết kĩ.

Bạn có tài liệu này dưới dạng PDF ko , cho mi`nh xin nhe' !

Xin cảm ơn,

[vnprodk]

Ai co tai lieu CCNA bang tieng viet cho minh xin dc khog? Hoc bang tieng A cung rat tot, nhung doc ko hieu dc het. Neu co ban tieng Viet nua thi tot qua cac bac ah!8-x

[Kakalot_]

Thank bạn Tranmyphuc1988,
Làm cái về vol 2 luôn cho cool.

hehehe......:)

[tranmyphuc]

Chapter 2: IPv6 Overview

IPv6 Addressing

IPv6 addresses are presented in 16-bit hexadecimal groups separated by colons. For example, 3ffe:1944:0100:000a:0000:00bc:2500:0d0b.
Shorthand rules:

• One group of all-zero segments can be presented with a double-colon (::)
• Leading zeros in each segment may be omitted

Subnet identification is performed in CIDR (bit count) notation (/64).
::/0 indicates an all-zeros or wildcard address.
::/128 represents an unspecified address.
Address Types

IPv6 addresses can be one of three types: unicast, anycast, or multicast.
Broadcast functionality is provided by the "all-nodes" multicast address.
Address types are identified by their leading bits:
BinaryHexType 11111111FF00::/8Multicast 11111110 10FE80::/10Link-local unicast 11111110 11FEC0::/10Site-local unicast (deprecated) 0012000::/3Global unicast (currently allocated) Global Unicast

A global unicast address is broken into three sections:

• Global routing prefix (48 bits)
• Subnet ID (16 bits)
• Interface ID (64 bits)

Local Unicast

Link-local unicasts are unique only to a single layer 2 link.
Site-local unicasts were defined in the original IPv6 standard bit have been replaced by Unique Local Addresses (FC00::/7) in RFC 4193.
Anycast

An anycast address is one address configured on multiple end nodes; dynamic routing will ideally forward traffic to the "nearest" or least-cost anycast server.
Any global unicast applied to more than one device can be considered any anycast address.
Multicast

A multicast address identifies a logical group of devices.
Multicast address structure:

• Multicast prefix (8 bits) - Always 0xFF
• Flags (4 bits)
• Scope (4 bits)
• Group ID (112 bits)

Address Scopes:

• 0x0 - Reserved
• 0x1 - Node-local
• 0x2 - Link-local
• 0x5 - Site-local
• 0x8 - Org-local
• 0xE - Global
• 0xF - Reserved

Embedded IPv4 Addresses

Different transition technologies have different ways of embedding an IPv4 address in an IPv6 address. Some examples for 10.23.1.5 are:

• FE80::5EFE:10.23.1.5 (ISATAP)
• ::FFFF:10.23.1.5 (SIIT)
• FEC0:0:0:1::10.23.1.5 (TRT)
• 2002:0A17:0105::/48 (6to4)

IPv6 Header

IPv6 headers have a fixed 40-byte length.
Header format:

• Version (4 bits) - Always set to 6
• Traffic class (8 bits) - DiffServ Code Point (DSCP)
• Flow label (20 bits) - An arbitrary field for differentiating traffic flows
• Payload length (16 bits) - Indicates the length of the payload (header length is not included)
• Next header (8 bits) - Identifies the extension header or upper-layer protocol that follows
• Hop limit (8 bits) - Decrementing hop counter (TTL)
• Source address (128 bits)
• Destination address (128 bits)

Extension Headers

Extensions headers provide for optional extended capabilities such as hop-by-hop options and IPsec encryption.
Next header values:

• 0 - Hop-by-hop options
• 43 - Routing
• 44 - Fragment
• 50 - ESP
• 51 - AH
• 59 - No next header
• 60 - Destination options

If a header is the last in the stack, its next header field will identify the upper-layer protocol that follows (e.g. 6 for TCP or 17 for UDP).
RFC 1883 specifies the order in which extensions headers should appear if they are used.
ICMPv6

IPv6 implements its own version of ICMP, defined in RFC 2463.
Like ICMPv4, ICMPv6 uses type/code pairings to identify field types.
Common field types:

• 1 - Destination unreachable
• 2 - Packet too big
• 3 - Time exceeded
• 4 - Parameter problem
• 128 - Echo request
• 129 - Echo reply
• 130 - Group membership query
• 131 - Group membership report
• 132 - Group membership reduction

Neighbor Discovery Protocol (NDP)

NFP is defined in RFC 2461
NDP functions:

• Router discovery
• Prefix discovery
• Parameter discovery - Link MTU, etc.
• Address autoconfiguration - Replaces DHCP
• Address resolution - Replaces ARP
• Next-hop determination - Link-layer address for next hop
• Neighbor unreachability detection
• Duplicate address detection
• Redirect - A router can inform a host of a better path out of the link

NDP uses ICMPv6 to exchange messages.
NDP messages types:

• Router Solicitation (RS) (Type 133) - Sent by hosts to request an RA
• Router Advertisement (RA) (Type 134) - Originated by routers to announce their existence
• Neighbor Solicitation (NS) (Type 135) - Facilitates link-layer address resolution and duplicate address detection
• Neighbor Advertisement (NA) (Type 136) - Response to an NS
• Redirect (Type 137) - Used by a router to inform a host of a better path out of the link

Address Autoconfiguration

On broadcast links, the interface ID (the second half of an IPv6 address) can be automatically generated by converting a 48-bit MAC address to a 64-bit EUI-64 address.
MAC-to-EUI64 conversion:

1. 0xFFFE is inserted between the two 24-bit halves of the MAC
2. The Universal/Local bit (7th bit) is flipped from 0 to 1

For example, 0000:0A0B:1234 becomes 0200:0AFF:FE0B:1234.
An EUI-64 identifier can be joined with a link-local prefix (FE80::/10) to form a complete link-local address.
A host can receive a global IPv6 address using either stateful or stateles autoconfiguration.
Stateful autoconfiguration uses DHCPv6 to request an IPv6 address from a server.
In stateless autoconfiguration, a host simply adds its interface ID to a prefix received in a router advertisement (RA).
Duplicate Address Detection (DAD)

DAD is performed on initial configuration of all addresses except anycasts.
New addresses are marked as tentative and cannot be used until they have been verified.
Neighbor Address Resolution

Layer 2 information for IPv6 neighbors is stored in the neighbor cache (similar to the ARP cache for IPv4).
Privacy Addresses

RFC 3041 defines IPv6 privacy addresses to alleviate privacy concerns over using a static, globally unique identifier (MAC address) as the interface ID.
Privacy addresses use a randomly-generated interface ID, which changes on a regular basis and/or when a new prefix is received.

[tranmyphuc]

Chapter 3: Static Routing

A routing table can be populated in three ways:

• Subnets gleaned from directly connected networks
• Manual configuration (static routes)
• Automatically via one or more dynamic routing protocols

A route's next hop must be reachable for the route to take effect.
Configuring Static Routes

IPv4:

Router(config)# ip route   [] []
Router(config)# ip route 172.16.0.0 255.255.0.0 192.168.1.1
Router(config)# ip route 10.0.0.0 255.0.0.0 Serial0/0 192.168.2.2

Specifying only an outbound interface rather than a next-hop address assumes that the destination network is directly connected to that interface.
IPv6:

Router(config)# ipv6 route / [] []
Router(config)# ipv6 route fec0::8:0:0:0:0/64 fec0::1:204:c1ff:fe50:f1c0
Router(config)# ipv6 route fec0::4:0:0:0:0/64 Serial0/0 fec0::2:2b0:ca4ff:fe73:459

IPv6 requires the next-hop address to be specified when configuring a route destined out a broadcast (Ethernet) interface.
Advanced Static Routing

Floating Static Routes

A floating static route is one configured with a higher administrative distance. It will only be used if more preferable routes for a destination fail.
Load Sharing

Multiple static routes can be configured to support equal-cost load sharing.
By default, Cisco Express Forwarding (CEF) performs load balancing per source-destination pair; all packets from one source to one destination will traverse one interface.
CEF also supports per-packet load balancing for IPv4 traffic.
The CEF load-balancing method can be adjusted:

Router(config)# ip load-sharing {per-destination | per-packet}

Recursive Lookups

A recursive lookup occurs when a route points to network not directly connected; one or more subsequent lookups are required to determine the next hop.
Troubleshooting Static Routes

Remember to verify both directions of traffic flow when tracing a path.
When a router or interface hardware is replaced, a new EUI-64 identifier will be used; this may require redefining a static route.

[tranmyphuc]

Chapter 5: Routing Information Protocol (RIP)

There are two versions of RIP:

• RIPv1 - Classful
• RIPv2 (or RIPng) - Classless

RIPv1 is defined in RFC 1058, and operates on UDP port 520.
RIP uses only hop count as its metric, with a maximum of 15 (a metric of 16 indicates unreachability).
Upon initialization, RIP routers issue requests for routes from neighbors. Neighbors issue responses containing their full tables.
Routers broadcast their entire table to the link-local broadcast address of 255.255.255.255 every 30 seconds (on average; a small jitter is included to prevent simultaneous flooding).
Timers

• Update (30 seconds) - How often routes are advertised (+/- a small random delay)
• Invalid (180 seconds) - How long a received route will stay in the table without being received again, before being marked as invalid.
• Flush (240 seconds) - 60 seconds longer than the invalid timer; invalid routes will be flushed from the table when this timer is reached.
• Holddown (180 seconds) - Routes will be kept in the table for this time before being replaced by an advertisement with a higher metric.

Timer configuration:

Router(config-router)# timers basic

Header Format

• Command (8 bits) - 1 for requests, 2 for responses
• Version (8 bits)

The header is followed by 1-25 route entries, each consisting of an address family identifier (set to 2 for IP), network address, and metric.
Configuration

Network configuration:

Router(config)# router rip
Router(config-router)# network 
Router(config-router)# network ...

Designating passive interfaces:

Router(config-router)# passive-interface Serial0/0

Specifying neighbors to unicast advertisements:

Router(config-router)# neighbor

An offset list can be implemented to artificially increase the metric for certain routes:

Router(config-router)# offset-list  {in | out}

Triggered extensions (defined in RFC 2091) can be enabled per interface to eliminate periodic updates:

Router(config-if)# ip rip triggered

[tranmyphuc]

Chapter 6: RIPv2, RIPng, and Classless Routing

RIPv2

RIPv2 (defined in RFC 1723) expands on its predecessor to support:

• Classless routing
• Authentication
• Next hop addresses
• External route tags
• Multicast advertisements (to 224.0.0.9) instead of broadcasts

RIPv2 uses space that was unused in the RIPv1 header to embed a 16-bit route tag in the header, and subnet mask and next hop information in each route entry.
RIPv2 can be run in compatibility mode, broadcasting advertisements to ensure backward compatibility with RIPv1.
Authentication can be implemented by inserting a plaintext password or MD5 hash before the first route entry in every advertisement.
RIPng

Next-Generation RIP (RIPng) is an entirely new protocol designed for IPv6; it does not support IPv4.
RIPng uses the same timers, procedures, message types, and metric as RIPv2.
A next hop address is included in a single designated route entry, and all entries which follow it are assumed reachable by that address.
Configuring RIPv2

Base configuration:

Router(config)# router rip
Router(config-router)# version 2
Router(config-router)# network 
Router(config-router)# network ...

By default, RIPv2 summarizes on classful boundaries. This can be disabled:

Router(config-router)# no auto-summary

The version of RIP advertisements sent and listened for can be configured per interface:

Router(config-if)# ip rip send version {1 | 2}
Router(config-if)# ip rip receive version {1 | 2}

Key chains can be used to implement authentication per interface:

Router(config-if)# ip rip authentication key-chain 
Router(config-if)# ip rip authentication mode md5

Configuring RIPng

IPv6 routing is required to support RIPng:

Router(config)# ipv6 unicast-routing

RIPng is enabled per interface rather than in global config:

Router(config-if)# ipv6 rip  enable

Details can be modified per RIPng process:

Router(config)# ipv6 router rip 
Router(config-router)# port  multicast ff02::9
Router(config-router)# distance

RIPng can be configured to artificially increment the metric per interface:

Router(config-if)# ipv6 rip  metric-offset

Enabling summarization:

Router(config-if)# ipv6 rip  summary-address /

[tranmyphuc]

Chapter 7: Enhanced Interior Gateway Routing Protocol (EIGRP)

EIGRP is an advanced version of Cisco's proprietary IGRP.
EIGRP runs the Diffusing Update Algorithm (DUAL) instead of Bellman-Ford to attain fast convergence while remaining loop-free.
Protocol-dependent modules are used to support protocols other than IP (such as IPX and AppleTalk).
Reliable Transport Protocol (RTP) provides ordered delivery of packets between EIGRP neighbors.
EIGRP can consider bandwidth, delay, reliability, and load in calculating a metric; only bandwidth and delay are considered by default.
EIGRP packet types:

• Hello - Peer discovery and maintenance
• Acknowledgment - Empty hello packets used to acknowledge messages
• Update - Convey route information
• Query - Request for a route
• Reply - Answer to a query

The default hello interval is 5 seconds on a fast link or 60 seconds on a slow (<= T1) link; this can be adjusted with ip hello-interval eigrp at interface configuration.
Each hello packet includes a hold time (three times the hello interval by deault); this an be adjusted with ip hold-time eigrp at interface configuration.
DUAL

Of all routes to a destination, the one with the lowest metric will be designated the successor route.
The feasibility condition states that a route's advertised distance must be less than the router's feasible distance to a destination for it to be considered a feasible successor, to avoid creating a routing loop.
Traffic will be load-balanced across multiple paths with the same feasible distance.
DUAL Finite State Machine

Routes remain in the passive state while no DUAL calculations are being performed.
An input event such as an interface state transition or the reception of an update, query, or reply packet, will cause the router to recalculate the distance for all its feasible successors for the affected route.
If a feasible successor cannot be found, the route enters the active state, and queries for a new path are issued to EIGRP neighbors.
If a router does not receive responses from all neighbors to which it issued queries within the active timer (3 minutes by default), the route is considered stuck in active, and unresponsive neighbors are removed from the neighbor table.
If all replies are received, the router calculates the feasible distance for all advertised routes, and adds the lowest valid route (if any) as the new successor.
Packet Header

EIGRP is IP protocol 88.
Header format:

• Version (8 bits)
• Opcode (8 bits) - Packet type (hello, update, etc.)
• Checksum (16 bits) - Error detection for the packet
• Flags (32 bits)
• Sequence (32 bits) - Sequence number used by RTP
• ACK (32 bits) - Last sequence number from neighbor
• Autonomous System (AS) Number (32 bits)

Type/Length/Value (TLVs) follow the header to provide routes and other information.
Configuring EIGRP

Base configuration:

Router(config)# router eigrp 
Router(config-router)# network  []

EIGRP will automatically load-balance across up to 16 equal-cost links. Unequal-cost balancing can be enabled by specifying a multiplier by which metrics may differ:

Router(config-router)# variance

The maximum number of paths used in load balacing can be configured:

Router(config-router)# maximum-paths

To designate a passive interface:

Router(config-router)# passive-interface

EIGRP summarizes a classful boundaries by default. To disable auto summarization:

Router(config-router)# no auto-summary

Routers can be configured as stubs to limit the types of routes advertised:

Router(config-router)# eigrp stub {connected | redistributed | static | summary |
 receive-only}

Neighbors do not send queries to stub routers.
Summarization boundaries can be implemented at interfaces:

Router(config-if)# ip summary-address eigrp

EIGRP only supports MD5 authentication, which is enabled per interface: 
 Router(config-if)# ip authentication key-chain eigrp  
Router(config-if)# ip authentication mode eigrp  md5