11-17-2014 09:54 PM - edited 03-05-2019 12:11 AM
Hi All,
I have router with 2 Connection.
1) IP Transit from Tier 2 Provider
2) IX - Local Internet Exchange for local peering
I'm receiving full internet route nearly 500k+ entries. I also have few local peering through IX connection to local telco. Now that , Im receiving more specific route from IP Transit link compared to local peering . Eg
Local Peer A( ASN YYYY) send route : a.a.0.0/16
IP Transit send route : a.a.1.0/24
With this , My traffic to a.a.1.0/24 end up routed over IP transit link. But we need the traffic routed via IX Peering, since its direct peering and have low latency and high bandwidth capacity.
Im thinking, to filter AS-PATH YYYY from IP Transit link, so that anyy traffic to ASN YYYY will now routed over local IX Peering. But, this will cause traffic get dropped if My Port to IX or Peering Partner Port to IX is went down. The traffic then should routed over IP transit link if local peering is down. Meaning to say , AS-Path filtering should be removed if local peering to that ASN is down.
Any Idea how to accomplish this ?
11-18-2014 01:29 AM
Hello
You dont say if this is just one router with two perrings or two routers with ibgp between them each with a isp peering?
However i for outbound traffic you can use either Weight or local Prefeance path selection for your local traffic to be go over your selected link.
For inbound As-Path prepending would be apllcable I think
Outbound:
--------------------
Weight (Is locally significant - Just one router)
access-list 10 permit x.x.x.x y.y.y.y
route-map Weight permit 10
match ip address 1
set weight 400000
route-map Weight permit 99
router bgp xx
neigbour x.x.x.x route-map Weight out (to ebgp perring for your prefered choice path)
or
route-map Local-Pref permit 10 ( for IBGP routers)
match ip address 1
set local-preferance 200
route-map Local-Pref permit 99
router bgp xx
neigbour x.x.x.x route-map Local-Pref in (to ebgp perring for your prefered choice path)
Inbound
-------------
AS=PAth prepend
route-map AS-Path permit 10
match ip address 10
set as-path prepend ASN ASN ASN
route-map AS-Path permit 99
router bgp xx
neigbour x.x.x.x route-map AS-Path out ( to the least preffered ISP)
res
Paul
11-18-2014 01:46 AM
Hi,
Its single router. Your solution is workable only if two route with same subnet mask received from two BGP neighbour. But, is this case its not, because IP Transit link receiving more specific route than my IX peering. But I need the traffic to be sent over IX Peering since its direct peering The first rule in route selection is longest matching bits regardless of which routing protocol used.
11-18-2014 02:35 AM
Hi Nagiswaren,
You can use advertise-map with Non-exist MAP in BGP.
if a.a.0.0/16 route do not exist then advertise a.a.1.0/24 subnet so BGP will not add subnet a.a.1.0/24 in table until route a.a.0.0/16 is missing from table.
Please rate the post if it solves your problem.
Thanks
Mahi
11-18-2014 02:40 AM
Hi Mohinder,
Im not sure how this will work, because im not originator of this route and im not advertising to anybody. This route i'm receiving from two different Peering Neighbour
11-18-2014 04:22 AM
HI Nagis,
it work in 2 ways. it will remove route from table so even not advertising to neighbor but it will remove from local routing table also.
Thanks
Mahi
11-18-2014 06:02 AM
Hi Mahi,
Thanks . Thats could solve my solve problem in small scale.. But im having the same problem for more than 1000 prefix.. I did some trick, but not sure if it best solution.
I have applied as-path filtering in IP Transit BGP peering, so that I wont receive any prefix same as local peering from this neighbour. To overcome traffic get dropped if local peering down, i have added static default route via IP Transit link,
11-19-2014 12:47 AM
Hi Nagis,
Thanks for the update. I think that will work as well fine.
Thanks
Mahi
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