04-08-2013 05:57 AM - edited 03-04-2019 07:31 PM
I have an issue where I am migrating from one location to another.
I want to advertise the same prefix from two seperate sites but I want to advertise individual unicast addresses from separate sites
This is where I am at, any help would be much appreciated as I can't seem to get this to work. All the traffic is just routed to one site. I do have the other site as backup but not as the primary for individual routes
ip access-list standard Denied-SiteA
permit host 192.168.1.1
permit host 192.168.1.2
ip access-list standard Allowed-SiteA
permit 192.168.1.0 0.0.0.255
ip access-list standard Allowed-SiteB
permit any
route-map SiteA permit 10
match ip address Denied-SiteA
set as-path prepend 11111 11111
route-map SiteA permit 20
match ip address Allowed-SiteA
set as-path prepend 11111
route-map SiteA permit 30
match ip address SiteB
set as-path prepend 11111 11111
router bgp xxxxx
neighbor xxxx route-map SiteA out
end
************************************************************
ip access-list standard Denied-SiteA
permit host 192.168.1.1
permit host 192.168.1.2
ip access-list standard Allowed-SiteA
permit 192.168.1.0 0.0.0.255
ip access-list standard Allowed-SiteB
permit any
route-map SiteB permit 10
match ip address Denied-SiteA
set as-path prepend 22222
route-map SiteB permit 20
match ip address Allowed-SiteA
set as-path prepend 22222 22222
route-map SiteB permit 30
match ip address SiteB
set as-path prepend 22222
router bgp xxxxx
neighbor xxxx route-map SiteB out
end
Solved! Go to Solution.
04-08-2013 11:48 AM
Hi Simon,
You should still be able to do the following:
advertise from site A:
192.168.1.0/24
192.168.1.100/32
192.168.1.105/32
Advertise from site B:
192.168.1.0/24
192.168.1.1/32
192.168.1.2/32
And prepend only on 192.168.1.0/24 depending on which site you want to prefer.
Hope this helps
04-08-2013 07:34 AM
Hi Simon,
Can you please more information. Are these site connected to the Internet or a private network. If they are connected to the Internet, the /32 prefixes will likely not make it beyond your ISP because of prefix filtering on the Internet. In this case only the /24 would be seen on the Internet.
Regards
04-08-2013 07:43 AM
Hi
Its a private MPLS cloud. I am advertising the routes to other sites within the same cloud.
Thanks
04-08-2013 07:52 AM
Thanks for the info. I see in the route-map that you advertise 192.168.1.1/32 and 192.168.1.2/32 but I do not see 192.168.100/32 and 192.168.1.105/32 being advertised on the other side. Can you please provide the complete bgp config from both side.
04-08-2013 08:22 AM
I don't have a complete BGP configuration to post as its a production environment, that I have replicated in my lab and I have modified the IP address to post here
I was hoping that 192.168.1.100 and 105 would be caught under permit 192.168.1.0 0.0.0.255 (i put them in purely to illustrate different IPs and can see that might be a bit confusing)
I was hoping to have site A as the primary path for the 192.168.1.x subnet (except for 192.168.1.1 and .2). Everything else including 192.168.1.1 and .2 via Site B
Location | Primary | Secondary | |
192.168.1.1 | Site B | prepended 22222 | prepended 11111 11111 |
192.168.1.2 | Site B | prepended 22222 | prepended 11111 11111 |
192.168.3-254 | Site A | prepended 11111 | prepended 22222 22222 |
All other Routes | Site B | prepended 22222 | prepended 11111 11111 |
I have a backup path as the two data centres are linked. Each has dual MPLS but as an absolute fail over there is also a link between them.
I can't seem to fine tune my configuration so that individual addresses are removed from the main /24. Currently I go to one site only
Thanks for your replies.
04-08-2013 10:13 AM
Hi Simon,
I would recommend to just announce 192.168.1.0/24 from site A and just the more specific (192.168.1.1/32 and 192.168.1.2/32) from site B. This way site A would attract all traffic to 192.168.1.0/24 except for .1 and .2 and you would not need to play with the prepend at all.
Hope this help
04-08-2013 11:14 AM
I had thought about doing that with aggregate addressing but I was hoping for a way of not having to change the network statements
I want to scale this up to many prefixes, not just a single one.
Also I need a backup route to the second site, in case the primary fails, thats why I want the pre-pend
Either way thanks for responding, I appreciate the feedback
04-08-2013 11:48 AM
Hi Simon,
You should still be able to do the following:
advertise from site A:
192.168.1.0/24
192.168.1.100/32
192.168.1.105/32
Advertise from site B:
192.168.1.0/24
192.168.1.1/32
192.168.1.2/32
And prepend only on 192.168.1.0/24 depending on which site you want to prefer.
Hope this helps
04-08-2013 10:55 PM
Hi,
as Harold said, it should be possible to configure what you want.
But it's difficult to say what's wrongin your config without having it available.
So just guessing:
Are there the host routes (static I suppose) configured on your routers?
If not present in RIB, BGP can't advertise them.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide