cis185-mod4-RIPv2

Ch.4 – RIPv2

CCNP 1 version 3.0

Rick Graziani

Cabrillo College

Rick Graziani [email protected] 2

Note to instructors

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http://www.cabrillo.cc.ca.us/~rgraziani/• The username is cisco and the password is perlman for all of

my materials.

• If you have any questions on any of my materials or the curriculum, please feel free to email me at [email protected] (I really don’t mind helping.) Also, if you run across any typos or errors in my presentations, please let me know.

• I will add “(Updated – date)” next to each presentation on my web site that has been updated since these have been uploaded to the FTP center.

Thanks! Rick


Overview

Rick Graziani [email protected]

Classless Routing Protocols

“The true characteristic of a classless routing protocol is the ability to carry subnet masks in their route advertisements.” Jeff Doyle, Routing TCP/IP

Benefits:

• All-zeros and all-ones subnets

– - Although some vendors, like Cisco, can also handle this with classful routing protocols.

• VLSM

– Can have discontiguous subnets

– Better IP addressing allocation

• CIDR

– More control over route summarization


Classless Routing Protocols

Classless Routing Protocols:

• RIPv2

• EIGRP

• OSPF

• IS-IS

• BGPv4


Few RIP facts

• RIP still working on routers and hosts today.

• IP RIP derived from RIP by Xerox for its XNS protocol stack.

• Initially implemented in Berkeley UNIX routed program.

• RIPv1 – Charles Hedrick, RFC 1058, 1988

• RIPv2 – Gary Malkin, RFC 1723, 1994

• RIPng for IPv6 – Gary Malkin, RFC 2080, 1997 (proposed standard), extension to RIPv2 message format.

The Grim Router


RIP version 1

0 1 2 3 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| command (1) | version (1) | must be zero (2) |

+---------------+---------------+-------------------------------+

| address family identifier (2) | must be zero (2) |

+-------------------------------+-------------------------------+

| IP address (4) |

+---------------------------------------------------------------+

| must be zero (4) |

+---------------------------------------------------------------+

| must be zero (4) |

+---------------------------------------------------------------+

| metric (4) |

+---------------------------------------------------------------+

• Classful Routing Protocol, sent over UDP port 520

• Does not include the subnet mask in the routing updates.

• Automatic summarization done at major network boundaries.

• Updates sent as broadcasts unless the neighbor command is uses which sends them as unicasts.


RIP version 2

0 1 2 3 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| command (1) | version (1) | must be zero (2) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Address Family Identifier (2) | Route Tag (2) |

+-------------------------------+-------------------------------+

| IP Address (4) |

+---------------------------------------------------------------+

| Subnet Mask (4) |

+---------------------------------------------------------------+

| Next Hop (4) |

+---------------------------------------------------------------+

| Metric (4) |

+---------------------------------------------------------------+

• Classless Routing Protocol, sent over UDP port 520

• Includes the subnet mask in the routing updates.

• Automatic summarization at major network boundaries can be disabled.

• Updates sent as multicasts unless the neighbor command is uses which sends them as unicasts.


RIP v2 operation

• All of the operational procedures, timers, and stability functions of RIP v1 remain the same in RIP v2, with the exception of the broadcast updates.

• RIP v2 updates use reserved Class D address 224.0.0.9.


Issues addressed by RIP v2

The following four features are the most significant new features added to RIP v2:

• Authentication of the transmitting RIP v2 node to other RIP v2 nodes

• Subnet Masks – RIP v2 allocates a 4-octet field to associate a subnet mask to a destination IP address.

• Next Hop IP addresses – The inclusion of a Next Hop identification field helps make RIP v2 more efficient than RIP v1 by preventing unnecessary hops.

• Multicasting RIP v2 messages – Multicasting is a technique for simultaneously advertising routing information to multiple RIP or RIP v2 devices.


RIP v2 message format

• All the extensions to the original protocol are carried in the unused fields.

• The Address Family Identifier (AFI) field is set to two for IP. The only exception is a request for a full routing table of a router or host, in which case it will be set to zero.


RIP v2 message format

• The Route Tag field provides a way to differentiate between internal and external routes. (Not used by RIP, but can be used by BGP – later.)

• External routes are those that have been redistributed into the RIP v2.• The Next Hop field contains the IP address of a better next hop IP address if one

exists. Next hop on same subnet, that is metrically closer to the destination than the advertising router. (Rather than an IP redirect message)

• Metric indicates how many internetwork hops, between 1 and 15 for a valid route, or 16 for an unreachable route.


Compatibility with RIP v1

RFC 1723 defines a compatibility switch with four settings, which allows versions 1 and 2 to interoperate:

1. RIP v1, in which only RIP v1 messages are transmitted 2. RIP v1 Compatibility, which causes RIP v2 to broadcast its messages

instead of multicast them so that RIP v1 may receive them 3. RIP v2, in which RIP v2 messages are multicast to destination

address 224.0.0.9 4. None, in which no updates are sent

• RFC 1723 recommends that switches be configurable on a per-interface basis. (coming soon)


Classless route lookups

• Classful routing behavior, no ip classless, and classless routing behavior, the ip classless global commands.

• This will be discussed in our presentation on “The Routing Table.” There is a dierence


Classless route lookups

• Route aggregation and supernetting.• A much greater benefit of having a subnet mask associated with each

route is being able to use variable-length subnet masking (VLSM) and to summarize a group of major network addresses with a single aggregate address. – Greater detail in Module 5, EIGRP


Classless routing protocols

• The true defining characteristic of classless routing protocols is the capability to carry subnet masks in their route advertisements.

• “One benefit of having a mask associated with each route is that the all-zeros and all-ones subnets are now available for use.” – Cisco allows the all-zeros and all-ones subnets to be used with

classful routing protocols.


Authentication

• A security concern with any routing protocol is the possibility of a router accepting invalid routing updates.

• The Authentication Type for simple password authentication is two, 0x0002,

• The remaining 16 octets carry an alphanumeric password of up to 16 characters.

• Configuration is coming!

Authentication is supported by modifying what would normally be the first route entry of the RIP message


Authentication

• RFC 1723 describes only simple password authentication • Cisco IOS provides the option of using MD5 authentication instead of

simple password authentication. • Cisco uses the first and last route entry spaces for MD5 authentication

purposes.• MD5 computes a 128-bit hash value from a plain text message of

arbitrary length and a password.


Authentication


MD5 Authentication (FYI) http://www.cisco.com/en/US/tech/tk713/tk507/technologies_tech_note09186a00800b4131.shtml

1 2

3 4

5 6


Limitations of RIPv2

• Slow convergence and the need of holddown timers to reduce the possibility of routing loops.

Note: See CCNA 2 for review if needed.



• RIPv2 continues to rely on counting to infinity as a means of resolving certain error conditions within the network.

• Dependent upon holddown timers.• Triggered updates are also helpful.

Note: See CCNA 2 for review if needed.



• Perhaps the single greatest limitation that RIPv2 inherited from RIP is that its interpretation of infinity remained at 16.

• Redistributed RIPv2 static cost metrics. (later in redistribution)– The default value of 1 is just like RIP. – This metric remains constant, and can only be changed by the

administrator.– However, the default value can be manually adjusted by the network

administrator.


Basic RIPv2 configuration

Other:For RIP and IGRP, the passive interface command stops the router from

sending updates to a particular neighbor, but the router continues to listen and use routing updates from that neighbor. (More later.)

Router(config-router)# passive-interface interface

Default behavior of version 1 restored: Router(config-router)# no version


Compatibility with RIP v1

NewYork

interface fastethernet0/0

ip address 192.168.50.129 255.255.255.192

ip rip send version 1

ip rip receive version 1


ip address 172.25.150.193 255.255.255.240

ip rip send version 1 2


ip address 172.25.150.225 225.255.255.240

router rip

version 2

network 172.25.0.0

network 192.168.50.0

• Interface FastEthernet0/0 is configured to send and receive RIP v1 updates.

• FastEthernet0/1 is configured to send both version 1 and 2 updates.

• FastEthernet0/2 has no special configuration and therefore sends and receives version 2 by default.

RIPv2


Discontiguous subnets and classless routing

• RIP v1 always uses automatic summarization.

• The default behavior of RIP v2 is to summarize at network boundaries the same as RIP v1.

router ripversion 2no auto-summary


Configuring authentication

Router(config)#key chain RomeoRouter(config-keychain)#key 1Router(config-keychain-key)#key-string Juliet The password must be the same on both routers (Juliet), but the name of the key

(Romeo) can be different.

Router(config)#interface fastethernet 0/0Router(config-if)#ip rip authentication key-chain RomeoRouter(config-if)#ip rip authentication mode md5

• If the command ip rip authentication mode md5 is not added, the interface will use the default clear text authentication. Although clear text authentication may be necessary to communicate with some RIP v2 implementations, for security concerns use the more secure MD5 authentication whenever possible.


Show commands


show ip rip database

Router# show ip rip database172.19.0.0/16 auto-summary172.19.64.0/24 directly connected, Ethernet0172.19.65.0/24[1] via 172.19.70.36, 00:00:17, Serial1[2] via 172.19.67.38, 00:00:25, Serial0172.19.67.0/24 directly connected, Serial0172.19.67.38/32 directly connected, Serial0172.19.70.0/24 directly connected, Serial1172.19.86.0/24[1] via 172.19.67.38, 00:00:25, Serial0[1] via 172.19.70.36, 00:00:17, Serial1

• The show ip rip database command to check summary address entries in the RIP database.

• These entries will appear in the database if there are only relevant child or specific routes being summarized.

• When the last child route for a summary address becomes invalid, the summary address is also removed from the routing table.

Router#show ip rip database


Show commands


Debug commands


Summary


RIPv2 Example

Scenario:

• Discontiguous subnets

• VLSM

• CIDR

• Supernet to 207.0.0.0/8

e0

ISP

SantaCruz2SantaCruz1

192.168.4.20/30

172.30.1.0/24

Internet

s0

s0 s0

s1

172.30.100.0/24

e0

192.168.4.24/30

.21

.22

.25

.26

10.0.0.0/8

e0.1

.1.1

Lo0Lo0

172.30.110.0/24172.30.2.0/24 .1

.1

.1

static route to207.0.0.0/8

207.0.0.0/16207.1.0.0/16207.2.0.0/16207.3.0.0/16

etc.

` 172.30.200.16/28

172.30.200.32/28

Lo1

Lo2

With the default auto-summary on ISP, it will load balance for all packets destined for 172.30.0.0/16


SantaCruz1

router rip

network 172.30.0.0

network 192.168.4.0

version 2

no auto-summary

SantaCruz2

router rip

network 172.30.0.0

network 192.168.4.0

version 2

no auto-summary

ISP

router rip

redistribute static

network 10.0.0.0

network 192.168.4.0

version 2

no auto-summary

ip route 207.0.0.0 255.0.0.0 null0

e0

ISP


192.168.4.20/30

172.30.1.0/24

Internet

s0

s0 s0

s1

172.30.100.0/24

e0

192.168.4.24/30

.21

.22

.25

.26

10.0.0.0/8

e0.1

.1.1

Lo0Lo0

172.30.110.0/24172.30.2.0/24 .1

.1

.1


207.0.0.0/16207.1.0.0/16207.2.0.0/16207.3.0.0/16

etc.

` 172.30.200.16/28

172.30.200.32/28

Lo1

Lo2

RIPv2 Example


e0

ISP


192.168.4.20/30

172.30.1.0/24

Internet

s0

s0 s0

s1

172.30.100.0/24

e0

192.168.4.24/30

.21

.22

.25

.26

10.0.0.0/8

e0.1

.1.1

Lo0Lo0

172.30.110.0/24172.30.2.0/24 .1

.1

.1


207.0.0.0/16207.1.0.0/16207.2.0.0/16207.3.0.0/16

etc.

` 172.30.200.16/28

172.30.200.32/28

Lo1

Lo2

SantaCruz2#show ip route

172.30.0.0/16 is variably subnetted, 6 subnets, 2 masks

C 172.30.200.32/28 is directly connected, Loopback2


R 172.30.2.0/24 [120/2] via 192.168.4.21, 00:00:21, Serial0

R 172.30.1.0/24 [120/2] via 192.168.4.21, 00:00:21, Serial0

C 172.30.100.0/24 is directly connected, Ethernet0


192.168.4.0/30 is subnetted, 2 subnets

R 192.168.4.24 [120/1] via 192.168.4.21, 00:00:21, Serial0

C 192.168.4.20 is directly connected, Serial0

R 10.0.0.0/8 [120/1] via 192.168.4.21, 00:00:21, Serial0

R 207.0.0.0/8 [120/1] via 192.168.4.21, 00:00:21, Serial0

Examining a Routing Table

Supernet, classless routing protcols will route supernets (CIDR)


RIPv2: Sending and Receiving Updates

ISP#debug ip rip

RIP protocol debugging is on

ISP#01:23:34: RIP: received v2 update from 192.168.4.22 on Serial1

01:23:34: 172.30.100.0/24 -> 0.0.0.0 in 1 hops

01:23:34: 172.30.110.0/24 -> 0.0.0.0 in 1 hops

ISP#

01:23:38: RIP: received v2 update from 192.168.4.26 on Serial0

01:23:38: 172.30.2.0/24 -> 0.0.0.0 in 1 hops

01:23:38: 172.30.1.0/24 -> 0.0.0.0 in 1 hops

ISP#

01:24:31: RIP: sending v2 update to 224.0.0.9 via Ethernet0 (10.0.0.1)

01:24:31: 172.30.2.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 172.30.1.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 172.30.100.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 172.30.110.0/24 -> 0.0.0.0, metric 2, tag 0

01:24:31: 192.168.4.24/30 -> 0.0.0.0, metric 1, tag 0

01:24:31: 192.168.4.20/30 -> 0.0.0.0, metric 1, tag 0

<text omitted>

ISP(config)# line console 0

ISP(config-line)# logging synchronous

multicast

Includes mask


Adding a default Routes to RIPv2

e0

ISP


192.168.4.20/30

172.30.1.0/24

Internet

s0

s0 s0

s1

172.30.100.0/24

e0

192.168.4.24/30

.21

.22

.25

.26

10.0.0.0/8

e0.1

.1.1

Lo0Lo0

172.30.110.0/24172.30.2.0/24 .1

.1

.1


207.0.0.0/16207.1.0.0/16207.2.0.0/16207.3.0.0/16

etc.

` 172.30.200.16/28

172.30.200.32/28

Lo1

Lo2

ISP

router rip

redistribute static

network 10.0.0.0

network 192.168.4.0

version 2

no auto-summary

default-information originate

ip route 207.0.0.0 255.0.0.0 null0

ip route 0.0.0.0 0.0.0.0 10.0.0.2 etherenet0


Other RIPv2 Commands

Router(config-router)# neighbor ip-address

Defines a neighboring router with which to exchange unicast routing information. (RIPv1 or RIPv2)

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

Configures an interface to send/receive RIP Version 1 and/or Version 2 packets

Router(config-if)# ip summary-address rip ip_address ip_network_mask

Specifies the IP address and network mask that identify the routes to be summarized.

Authentication and other nice configuration commands and examples:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800d97f7.html

Ch.4 – RIPv2

CCNP 1 version 3.0

Rick Graziani

Cabrillo College

Date post:	12-Nov-2014
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