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Home > Archive > CCNP > November 2001 > Static Routes
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| whytokayok 2001-11-22, 9:14 pm |
| Has any one ever set up two static default routes on a router with one route having a higher administrative distance? I have three routers set up in a full mesh configuration. I'm trying to implement some redundancy if possible. | |
| sidodgers 2001-11-22, 11:25 pm |
| quote:
Originally posted by whytokayok
Has any one ever set up two static default routes on a router with one route having a higher administrative distance? I have three routers set up in a full mesh configuration. I'm trying to implement some redundancy if possible.
For all but the simplest configurations, this setup is suboptimal. Sure, you can do the following:
R1
ip route r2.0.0.0 255.255.255.0 r2 1
ip route r2.0.0.0 255.255.255.0 r3 10
ip route r3.0.0.0 255.255.255.0 r3 1
ip route r3.0.0.0 255.255.255.0 r2 10
R2
ip route r1.0.0.0 255.255.255.0 r1 1
ip route r1.0.0.0 255.255.255.0 r3 10
ip route r3.0.0.0 255.255.255.0 r3 1
ip route r3.0.0.0 255.255.255.0 r1 10
R3
ip route r1.0.0.0 255.255.255.0 r1 1
ip route r1.0.0.0 255.255.255.0 r2 10
ip route r2.0.0.0 255.255.255.0 r2 1
ip route r2.0.0.0 255.255.255.0 r1 10
where r# stands for the ip of your router and r#.0.0.0 represents the networks you are reaching through the said router, but this situation has the following problems:
- scalability; ie if you want to add more networks behind a given router, you need four (yes, that's it, four) routes (two on each other router) added for a given network
- reliability; you're banking on a router being able to work out that its connection to a peer is dead. without the use of an active routing protocol, this usually doesn't happen.
the way i'd accomplish the following is:
(for r2 and r3, substitute appropriately)
router ospf 100
network (subnet between r1 and r2) area 0
network (subnet between r1 and r3) area 0
network r1.0.0.0 0.0.0.255 area 1
area 1 stub no-summary
rinse and repeat for r2 and r3, putting r2.0.0.0 into area 2, and r3.0.0.0 into area 3. The routes will automatically be shared between the peers on the subnets in area 0, and the optimal paths will be utilised while they are available. The hello timer on OSPF ensures that each router will know if a peer is dead and send traffic via the suboptimal path.
Cheers,
Sid | |
| Yankee 2001-11-23, 9:24 am |
| Don't believe he stated he wasn't using a routing protocol so if that is true, the answer is yes you can do it and it works fine.
Yankee | |
| whytokayok 2001-11-23, 7:56 pm |
| Yes, I cannot use dynamic routing. My return links to R1 from R2 and R3 rely upon the DLCI and not the IP address. Therefore, as robust as BGP is it won't help. What I was trying to do is provide redundant default routes back to R1 in case one of the links goes down that feed either R2 or R3. R1 provides internet access for R2 and R3. | |
| sidodgers 2001-11-23, 8:32 pm |
| quote:
Originally posted by whytokayok
Yes, I cannot use dynamic routing. My return links to R1 from R2 and R3 rely upon the DLCI and not the IP address. Therefore, as robust as BGP is it won't help. What I was trying to do is provide redundant default routes back to R1 in case one of the links goes down that feed either R2 or R3. R1 provides internet access for R2 and R3.
hmm, sorry for misunderstanding.
in that case, what you're describing with floating static routes should work under certain circumstances. the important thing is that if a link fails, the router knows that it's failed and removes routes associated with it from the ip routing table. if this is the case, then the static route configuration i posted above should work without a trauma.
HTH 
Sid |
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