From: John Murphy (jt.murphy@comcast.net)
Date: Sun Mar 06 2005 - 00:25:25 GMT-3
I don't think you're missing anything, it's probably true that in some
(probably most) cases split-horizon needs to be disabled, I just
happened to find one case where it didn't. The point I was trying to
make, not very clearly I'm afraid, is don't just blindly believe the
documentation. Mock it up, test it, trust nothing, verify everything.
jm
Jongsoo.Kim@Intelsat.com wrote:
>John
>
>Wow, Now I am lost.
>
>Per CCO, no split-horizon should be issued for rip summary address to be
>advertised.
>http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_command_refe
>rence_chapter09186a008010a39d.html#wp1019063
>
>But your lab proved it wrong?
>
>What am I missing here?
>
>Regards
>
>Jongsoo
>
>-----Original Message-----
>From: John Murphy [mailto:jt.murphy@comcast.net]
>Sent: Saturday, March 05, 2005 9:57 PM
>To: Kim, Jongsoo
>Cc: ccielab@groupstudy.com
>Subject: Re: Summary address for rip
>
>
>Comments inline
>
>Jongsoo.Kim@Intelsat.com wrote:
>
>
>
>>I am sure many of you know about this.
>>This is totally news to me. ( I have obvioulsy underestimated the mighty
>>RIP!)
>>
>>As passive interface behaves differently between Rip and EIGRP, so does ip
>>summary-address.
>>For rip, Ip split-horizon has be to diable for summary-address to be
>>advertise, while EIGRP don't care about it.
>>
>>
>>
>>
>I agree that the documentation says this, however in practice it's not
>quite so clearcut.... this is on a router running 12.2(15)T12. Example
>below....
>
>
>[R2 --S2/0-]------------[-S2/0 --R4 --S2/0.13-]-------------[-S2/0--R3]
>
>R4#sh ip int Ser2/0.13
>Serial2/0.13 is up, line protocol is up
> Internet address is 172.10.43.4/24
> Broadcast address is 255.255.255.255
> Address determined by non-volatile memory
> MTU is 1500 bytes
> Helper address is not set
> Directed broadcast forwarding is disabled
> Multicast reserved groups joined: 224.0.0.14 224.0.0.17 224.0.0.1
>224.0.0.2
> 224.0.0.22 224.0.0.13 224.0.0.9
> Outgoing access list is not set
> Inbound access list is not set
> Proxy ARP is enabled
> Local Proxy ARP is disabled
> Security level is default
> Split horizon is enabled <<<<<<<<<<<<<<<<<<<<<<<<<<<< Split Horizon
>is enabled
>
>I added three /32 loopbacks on R4...
>
>!
>interface Loopback234
> ip address 172.10.200.234 255.255.255.255
>!
>interface Loopback235
> ip address 172.10.200.235 255.255.255.255
>!
>interface Loopback236
> ip address 172.10.200.236 255.255.255.255
>!
>I then configured the summary on Ser2/0.13
>
>interface Serial2/0.13 point-to-point
> ip address 172.10.43.4 255.255.255.0
> ip pim dense-mode
> ip summary-address rip 172.10.200.0 255.255.255.0
> frame-relay interface-dlci 403
> ip rsvp bandwidth 25 20
>!
>
>And on R3....
>R3#ship rip
> 172.10.0.0/16 is variably subnetted, 19 subnets, 6 masks
>R 172.10.200.0/24 [120/1] via 172.10.43.4, 00:00:06, Serial2/0
>R 172.10.25.0/29 [120/1] via 172.10.43.4, 00:00:06, Serial2/0
>R 172.10.25.64/26 [89/1] via 172.10.43.4, 00:00:06, Serial2/0
>
>
>It's just another IGP, don't let it psych you out....
>
>jm
>
>
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