03-21-2009 07:10 AM - edited 03-04-2019 04:01 AM
guys if we have two isp on one router.......so what is the way to send all routes to one isp and if it fails it shd go to other isp????
03-21-2009 07:17 AM
Default static to one ISP and floating default static pointing to the backup ISP.
ip route 0.0.0.0 0.0.0.0
ip route 0.0.0.0 0.0.0.0
03-21-2009 08:15 AM
Hello Khan,
if using BGP the right tool is
BGP conditional advertisement
see
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t4/feature/guide/ftbgpri.html#wp1023979
this way you can start to advertise to ISP2 only when first session fails
Hope to help
Giuseppe
03-21-2009 08:17 AM
Giuseppe:
Unnecessarily complicated.
He doesnt want load sharing. He wants hot/standby ISP redundancy.
Statics are the way to go, papi.
03-21-2009 02:13 PM
Victor, Giu
I have different suggestion.
the static default routs are never removed from the routing table unless the "Arp-cache" timed out, and this takes very long period by default.
Conditional Advertisment is also not required in his case.
I would recommend "Reliable Static routing with Object tracking" as an option
OR
Normal BGP.
HTH
Mohamed
03-21-2009 02:33 PM
I honestly would stay away from BGP because it doesnt buy you anything, just complicates the scenario.
The static route with object tracking sounds good, thinking off-the-cuff.
Victor
03-22-2009 01:02 AM
You really should use BGP for this. It would be pretty simple, just setup eBGP with weight command to dictate preferred ISP. Also, ensure both ISP's advertise default route to you (make sure you filter so as to not make your AS a transient one). You will also need to be sure that neither ISP is originating your networks, you want that to happen on your network.
The issue with object tracking and static routes is that obviously if you are not advertising your internal networks to each ISP, then they must be originating them. So, if the primary link goes down, depending on physical media, it is possible that the primary ISP would continue to advertise your routes, creating a black hole scenario.
Here are the configs that I would suggest. Then just ask your ISP's to advertise the default route over these BGP connections...
conf t
ip prefix-list defaultnet seq 5 permit 0.0.0.0/0
!
ip prefix-list deny_default seq 5 deny 0.0.0.0/0
ip prefix-list deny_default seq 10 permit 0.0.0.0/0 le 32
!
route-map Prepend deny 5
match ip prefix-list defaultnet
route-map Prepend permit 10
set as-path prepend xxxx xxxx xxxx xxxx xxxx xxxx xxxx
!
router bgp xxxx
network blah mask blah
network blah mask blah
...
neighbor 1.1.1.1 remote-as yyyy
neighbor 1.1.1.1 weight 200
neighbor 1.1.1.1 description *** ISP 1 | Primary ***
neighbor 1.1.1.1 prefix-list defaultnet in
neighbor 1.1.1.1 prefix-list deny_default out
!
neighbor 2.2.2.2 remote-as zzzz
neighbor 2.2.2.2 weight 100
neighbor 2.2.2.2 description *** ISP 2 | Backup ***
neighbor 2.2.2.2 prefix-list defaultnet in
neighbor 2.2.2.2 route-map Prepend out
end
wr
03-22-2009 08:20 PM
What would you guys recommend if load sharing is needed in this situation?
03-23-2009 03:56 AM
If load sharing is preferred, just check this forum, there are a bunch solutions here for that scenario.
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