Offset-List with RIP
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Forum Name: CCIE
Forum Discription: Discuss the CCIE written and lab here.
URL: http://certcities.com/forums/forum_posts.asp?tid=5092
Printed Date: 23 October 2007 at 8:14pm
Topic: Offset-List with RIP
Posted by: hudsonmbg
Subject: Offset-List with RIP
Date Posted: 25 June 2007 at 12:32am
Hi,
I have a 3 router topology consisting of RIP and OSPF. R4 is connected to SW2 (a 3560 running RIP) and to R5. SW2 connects to R4 and R5 while R4 connects to both SW2 and R5, with RIPv2 configured between them. There is an OSPF domain running on R5 and R5 generates a default route for the RIP networks to get to the OSPF domain.
I R4 to load balance traffic to the OSPF domain using both R5 and SW2. Presently, just the R5 route has been chosen and installed in the routing table.
I am using the offset-list command and the format is offset-list 0...command. I am not very conversant with this command. Should I apply it incoming and what interface should I apply this to? R4 connects directly to R5 on S0/1 and to SW2 on e0/1
Thanks,
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Bishop(TCP/IP), CCNP |
Replies:
Posted by: hudsonmbg
Date Posted: 25 June 2007 at 12:35am
As an Edit,
On the routing table, before offset is applied, the output looks like this
R* 0.0.0.0/0 [120/1] via 139.1.45.5 what metric is suitable when configuring the offset-list for load-balancing to occur?
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Bishop(TCP/IP), CCNP |
Posted by: Headhunter
Date Posted: 25 June 2007 at 12:37am
the in keyword is applied to routes learned from another router
the out keyword is used on routes the router advertises
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Koen
CCSI#30501 CCNP CCIP CCVP CCSP CCDP CQS-Cisco Wireless LAN Design & Support Cisco Unity Design Specialist Cisco IP Telephony Design Specialist JNCIA-ER MCSE MCSA:Messaging |
Posted by: Headhunter
Date Posted: 25 June 2007 at 12:38am
does RIP do unequal cost load balancing???
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Koen
CCSI#30501 CCNP CCIP CCVP CCSP CCDP CQS-Cisco Wireless LAN Design & Support Cisco Unity Design Specialist Cisco IP Telephony Design Specialist JNCIA-ER MCSE MCSA:Messaging |
Posted by: hudsonmbg
Date Posted: 25 June 2007 at 12:42am
In normal life, RIP doesn't but what happens if you tweak the metrics to make them look equal? That's the use of the offset-list command, I think. My question is what metric value is required to make it happen?
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Bishop(TCP/IP), CCNP |
Posted by: Headhunter
Date Posted: 25 June 2007 at 12:44am
15
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Koen
CCSI#30501 CCNP CCIP CCVP CCSP CCDP CQS-Cisco Wireless LAN Design & Support Cisco Unity Design Specialist Cisco IP Telephony Design Specialist JNCIA-ER MCSE MCSA:Messaging |
Posted by: hudsonmbg
Date Posted: 26 June 2007 at 2:15am
Hi I just had a response from some guy at Cisco and here is his explanation. I think it is good and also rhymes with the explanation you gave those different metric values:
offset-list {access-list-number | access-list-name} {in | out}
offset [interface-type interface-number]
I think the default route generated by R5 starts with a hop count of
one; to get an equal-cost multipath (and therefore load-shared) route
from RIP, you want R4 to observe default routes received on S0/1 and
increment their metric by the amount they are incremented on the
other path, which is to say by one. So I think you want something
like the following on R4
ip access-list standard default-route
permit 0.0.0.0 0.0.0.0
offset-list default-route in 1 S0/1
That should look at the default route coming on from R5 (and nothing
else) and increment its hop count by one, making IP then split the load.
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Bishop(TCP/IP), CCNP |
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