03-17-2010 06:37 AM - edited 03-04-2019 07:50 AM
Our proposed setup is the following. We are using the same ISP.
Corp RTR---->ISP (20MB)
|
| 100MB Metro LAN
|
DR RTR---->ISP (20MB)
We have been assigned a /24 block from our ISP and I would like to know the best design to load balance and failover to the Metro LAN in the event of a failure.
Am I correct in following the documentation from the link below?
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml#conf3
Thanks in advance.
Solved! Go to Solution.
03-17-2010 09:27 AM
Hello Igor,
I see.
I guess you have split the public /24 address block in two or more parts internally in your domain and that edge routers are advertising the /24 as a result of using an aggregate address or a static route to null0 for the /24 IP network.
if the ISP is only one you could try to setup an agreement in order to send also specific /25 routes with them.
the other /25 could be advertised with your own AS prepending
so it could be:
COrp: sends out first /25, aggregate /24 second /25 with As path prepending
Hosting: sends out second /25, aggregate /24, first /25 with AS path prepending
Example:
ip prefix-list firstblock seq 5 permit x.y.z.0/25
route-map CorpToISP permit 10
match ip address prefix firstblock
set as-path prepend yourAS yourAS
route-map CorpToISP permit 20
! second empty block to advertise the other prefixes
router bgp yourAS
neigh ISP-ipaddress route-map CorpToISP out
Hope to help
Giuseppe
03-17-2010 07:06 AM
Hello Igor,
you are correct in following that link an iBGP session over the metro ethernet link is useful in this case
if DR site should be used only used for failover you could use MED and As path prepending to make the first link the primary link.
route-map fromDRtoISP permit 10
set metric 500
set as-path prepend yourAS yourAS
DR router
router bgp yourAS
neigh ISP route-map fromDRtoISP out
Hope to help
Giuseppe
03-17-2010 07:11 AM
Giuseppe,
I should change DR to Hosting. Our end goal is to host clients and load balance our links as our /24 netblock will be used for clients at the hosting center and for our company at our HQ. In case of either Internet link failing, we would need traffic to use the other Internet link and the metro link.
Hope this makes sense.
Thanks
03-17-2010 09:27 AM
Hello Igor,
I see.
I guess you have split the public /24 address block in two or more parts internally in your domain and that edge routers are advertising the /24 as a result of using an aggregate address or a static route to null0 for the /24 IP network.
if the ISP is only one you could try to setup an agreement in order to send also specific /25 routes with them.
the other /25 could be advertised with your own AS prepending
so it could be:
COrp: sends out first /25, aggregate /24 second /25 with As path prepending
Hosting: sends out second /25, aggregate /24, first /25 with AS path prepending
Example:
ip prefix-list firstblock seq 5 permit x.y.z.0/25
route-map CorpToISP permit 10
match ip address prefix firstblock
set as-path prepend yourAS yourAS
route-map CorpToISP permit 20
! second empty block to advertise the other prefixes
router bgp yourAS
neigh ISP-ipaddress route-map CorpToISP out
Hope to help
Giuseppe
03-18-2010 08:02 AM
Giuseppe
Can you explain this command in more detail?
route-map CorpToISP permit 20
! second empty block to advertise the other prefixes
03-18-2010 08:29 AM
Hello Igor,
it is simply an empty route-map clause to be used to advertise the other IP prefixes to eBGP neighbor
route-map CorpToISP permit 20
>> ! second empty block to advertise the other prefixes
this is just a comment sorry if it caused confusion
Hope to help
Giuseppe
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