From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Mon Feb 21 2005 - 15:52:19 GMT-3
Look at the output of R1's "show ip protocols" and you can see that it
will receive RIPv1 and RIPv2 updates (default behavior). This means
that R1 will accept the RIPv2 updates sent from R3.
R1#sh ip proto
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 0 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: rip
Default version control: send version 1, receive any version
Interface Send Recv Triggered RIP Key-chain
Serial0.2 1 1 2
Serial0.3 1 1 2
Serial0.5 1 1 2
Serial1 1 1 2
^^^
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: anantha S [mailto:san.study@gmail.com]
Sent: Monday, February 21, 2005 10:23 AM
To: Brian Dennis
Cc: Cisco certification
Subject: Re: RIP v1 and v2 question
Hi Brian Dennis / Brian McGahan,
I have attached the router configs of R3 (ripv2) and R1 (ripv1). R3's
connected interface 10.50.31.0/24 is learnt over the link of
10.50.13.0/28 which is connected to R1 (ripv1).
My assumption was, Ripv1 router always checks with the connected
interface mask. and did not expect 10.50.31.0/24 in R1's routing
table.
R3
---R3# R3#sh run Building configuration...
Current configuration : 2182 bytes ! version 12.2 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname R3 ! enable password anik ! ip subnet-zero ip cef no ip domain-lookup ! ! key chain anik key 1 key-string anik ! ! ! ! interface Loopback1 ip address 13.13.13.13 255.255.255.0 ! interface Loopback2 ip address 133.133.133.133 255.255.255.0 ! interface Loopback3 ip address 10.50.13.97 255.255.255.240 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Loopback31 ip address 30.30.1.1 255.255.255.0 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Loopback32 ip address 30.30.2.1 255.255.255.0 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Loopback33 ip address 30.30.3.1 255.255.255.0 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Loopback34 ip address 30.30.4.1 255.255.255.0 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Loopback35 ip address 30.30.5.1 255.255.255.0 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Loopback36 ip address 30.30.6.1 255.255.255.0 ip ospf message-digest-key 1 md5 anik ip ospf network point-to-point ! interface Ethernet0 ip address 10.50.31.3 255.255.255.0 ip rip authentication mode md5 ip rip authentication key-chain anik ! interface Serial0 no ip address encapsulation frame-relay no frame-relay inverse-arp frame-relay lmi-type cisco ! interface Serial0.1 point-to-point ip address 10.50.13.3 255.255.255.240 ip ospf message-digest-key 1 md5 anik frame-relay interface-dlci 301 ! interface Serial0.2 point-to-point ip address 10.50.13.23 255.255.255.240 ip ospf message-digest-key 1 md5 anik frame-relay interface-dlci 302 ! interface Serial1 no ip address shutdown ! interface BRI0 no ip address encapsulation hdlc shutdown ! router rip version 2 network 10.0.0.0 no auto-summary ! ip classless ip http server ! access-list 31 permit 10.50.31.0 0.0.0.255 route-map conn permit 10 match ip address 31 ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! end R3# R3# R3# R3#sh ip protocols Routing Protocol is "rip" Sending updates every 30 seconds, next due in 13 seconds Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: rip Default version control: send version 2, receive version 2 Interface Send Recv Triggered RIP Key-chain Ethernet0 2 2 anik Loopback3 2 2 Serial0.1 2 2 Serial0.2 2 2 Automatic network summarization is not in effect Maximum path: 4 Routing for Networks: 10.0.0.0 Routing Information Sources: Gateway Distance Last Update 10.50.13.1 120 20:10:26 Distance: (default is 120)
R3# R3# R3# R3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks C 10.50.13.16/28 is directly connected, Serial0.2 C 10.50.31.0/24 is directly connected, Ethernet0 C 10.50.13.0/28 is directly connected, Serial0.1 C 10.50.13.96/28 is directly connected, Loopback3 13.0.0.0/24 is subnetted, 1 subnets C 13.13.13.0 is directly connected, Loopback1 133.133.0.0/24 is subnetted, 1 subnets C 133.133.133.0 is directly connected, Loopback2 30.0.0.0/24 is subnetted, 6 subnets C 30.30.1.0 is directly connected, Loopback31 C 30.30.2.0 is directly connected, Loopback32 C 30.30.3.0 is directly connected, Loopback33 C 30.30.4.0 is directly connected, Loopback34 C 30.30.5.0 is directly connected, Loopback35 C 30.30.6.0 is directly connected, Loopback36 R3#
R1: ---- R1#sh run Building configuration...
Current configuration : 1279 bytes ! version 12.2 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname R1 ! ! ip subnet-zero ip cef no ip domain-lookup ! ! ! ! ! interface Loopback1 ip address 11.11.11.11 255.255.255.0 ! interface Loopback2 ip address 111.111.111.111 255.255.255.0 ! interface Ethernet0 no ip address shutdown ! interface Serial0 no ip address encapsulation frame-relay no frame-relay inverse-arp frame-relay lmi-type cisco ! interface Serial0.2 point-to-point ip address 10.50.13.41 255.255.255.240 ip ospf message-digest-key 1 md5 anik frame-relay interface-dlci 102 ! interface Serial0.3 point-to-point ip address 10.50.13.1 255.255.255.240 ip ospf message-digest-key 1 md5 anik frame-relay interface-dlci 103 ! interface Serial0.5 point-to-point ip address 10.50.13.131 255.255.255.224 frame-relay interface-dlci 105 ! interface Serial1 ip address 10.50.13.81 255.255.255.240 ip ospf message-digest-key 1 md5 anik ! interface BRI0 no ip address encapsulation hdlc shutdown ! router rip network 10.0.0.0 no auto-summary ! ip classless ip route 10.10.45.0 255.255.255.0 10.50.13.84 ip route 10.10.45.0 255.255.255.0 10.50.13.135 200 ip http server ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 ! end
R1# R1# R1# R1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route
Gateway of last resort is not set
111.0.0.0/24 is subnetted, 1 subnets C 111.111.111.0 is directly connected, Loopback2 10.0.0.0/8 is variably subnetted, 8 subnets, 3 masks C 10.50.13.32/28 is directly connected, Serial0.2 R 10.50.13.16/28 [120/1] via 10.50.13.3, 00:00:25, Serial0.3 R 10.50.31.0/24 [120/1] via 10.50.13.3, 00:00:25, Serial0.3 S 10.10.45.0/24 [1/0] via 10.50.13.84 C 10.50.13.0/28 is directly connected, Serial0.3 R 10.50.13.96/28 [120/1] via 10.50.13.3, 00:00:25, Serial0.3 C 10.50.13.80/28 is directly connected, Serial1 C 10.50.13.128/27 is directly connected, Serial0.5 11.0.0.0/24 is subnetted, 1 subnets C 11.11.11.0 is directly connected, Loopback1 R1# R1# R1# R1# R1# R1#sh ip proto Routing Protocol is "rip" Sending updates every 30 seconds, next due in 0 seconds Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: rip Default version control: send version 1, receive any version Interface Send Recv Triggered RIP Key-chain Serial0.2 1 1 2 Serial0.3 1 1 2 Serial0.5 1 1 2 Serial1 1 1 2 Automatic network summarization is not in effect Maximum path: 4 Routing for Networks: 10.0.0.0 Routing Information Sources: Gateway Distance Last Update 10.50.13.3 120 00:00:02 Gateway Distance Last Update 10.50.13.135 120 00:00:15 Distance: (default is 120)
R1# R1# R1#
On Mon, 21 Feb 2005 05:53:57 -0500, Brian Dennis <bdennis@internetworkexpert.com> wrote: > Since RIPv1 is incapable of carrying the subnet mask information, how > could R1 check the "mask" of the 10.50.31.0 route? Post a "show ip > route 10.50.31.0" from R1 and see if its not showing up as > 10.50.31.0/28. > > Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security) > > bdennis@internetworkexpert.com > Internetwork Expert, Inc. > http://www.InternetworkExpert.com > Toll Free: 877-224-8987 > Direct: 775-745-6404 (Outside the US and Canada) > > -----Original Message----- > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of > anantha S > Sent: Sunday, February 20, 2005 2:15 PM > To: Cisco certification > Subject: RIP v1 and v2 question > > Hi all, > > Question about Rip v1 router accepting a route of different mask from > the received interface which has same major network. > > Topology: > ---------------- > 10.50.13.128/27-------R1 (rip v1)-----10.50.13.0/28------R3 (rip > v2)---10.50.31.0/24 > > Should R1 learn 10.50.31.0/24 ? > > Some reason R1 is learning the route. Can someone give me the reason ? > I thought it should check for the major network and mask in R1 > against 10.50.31.0/24 versus 10.50.13.0/28 and it should reject the > update. > > Below are the snippet i read ((i think its specific to rip version 1)) > ------------------------------------------------------------------------ > ---------------------- > > Send Updates > ------------------------ > Before Router 1 sends updates to Router 2, it checks the following: > b" Is the subnet information part of the same major net as the > interface that is sourcing the update? > o No. Router 1 summarizes at the major net boundary and advertises > the network. > o Yes. Does the network have the same subnet mask as the interface > that is sourcing the update? > o' No. Router 1 drops the network, and does not advertise it. > o' Yes. Router 1 advertises the subnet. > > Receive Updates > --------------------------- > When RIP or IGRP receive an update, they perform certain checks before > accepting the update and applying the subnet mask. Below is the > sequence of events that occurs before Router 2 accepts an update from > Router 1: > b" Is the subnet received in the update on the same major net as > the > interface that received the update? > o Yes. Router 2 applies the mask of the interface that received > the > update. If the advertised network has a host bit set in the host > portion of the update, Router 2 applies the host mask (/32). In the > case of RIP, it continues to advertise the /32 route to the subsequent > router, but IGRP does not. > o No. Do any subnets of this major net already exist in the > routing > table, known from interfaces other than the one that received the > update? Note that the network in this update should be a major net > unless the link between the two routers is an unnumbered link, in > which case it is possible for the update to contain subnet > information. > o' Yes. Router 2 ignores the update. > o' No. Router 2 applies a classful mask. If the update came across > an > unnumbered link and contains subnet information (bits in subnet > portion of network are set), then Router 2 applies a host mask. Please > refer to Understanding and Configuring the ip unnumbered Command for > unnumbered case examples. > >
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