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Community Member

Continued from an OLd Posting-BGP advertise problem-Ques.

Greetings,

I am posting this as part of an old posting on this issue but in a different context. I didn't get response from old posting and my time is running out! I wanted some expert advise on my decision please. forgive for new posting please.

I am trying to bring up these new network, with two border router using BGP to two different providers and want to have redundancy and Load sharing.

the last time I brough it up, the network collapsed due to a hardware failure (SUP 720 went bad) but what I noticed during a few hours of operation was that, i was dending traffic out the Abovenet connection (the router that went bad) and no traffic was going out the other router although I was advertising and the bGP session was up with no problems! I am sure that the redundancy was there but no load sharing.

i the BGP config i have posted here, I did include one /20 block on one router but didn't include it on the other one, the other three bocks as on both. /19 and 20 on one, and /19 and 20 on the other. so the block that has not been advertised on both and only on one has to flow out or th etraffic from that block has to flow out the other router but if that router goes down, that block won't flow out any more and need to be added manually to the other one.

Now, I am trying to fine a way for both the redundancy and load sharing without having to deal with this problem?

I have seen many documents and books but none seem to be fitting my scenario or I may not be able to find a fit or choose from all the different types of advertising and filtering!!?

I really appreciate if you guys can help me out here please.

The files are attached.

Regards,

Masood

8 REPLIES
Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

This is the template I normally used for multihomed customer(two isps) with two exit routers

R1)

router bgp xxxx

no synchronization

bgp log-neighbor-changes

neighbor <1.1.1.1> remote-as 12

neighbor <1.1.1.1> route-map SET-LP in

neighbor <1.1.1.1> route-map SET-MED out

route-map SET-LP permit 10

match ip prefix-list New1-x.x.xblock<<<<<<<<<<<

Set local-preference 250

route-map SET-LP permit 20

Set local-preference 200

route-map SET-MED

set metric 50

ip prefix-list New1-x.x.xblock permit 198.a.a.0/24

ip prefix-list New1-x.x.xblock permit 216.d.d.240.0/20

R2)

router bgp xxxx

no synchronization

bgp log-neighbor-changes

neighbor <2.2.2.2> remote-as 21

neighbor <2.2.2.2> route-map SET-LP in

neighbor <2.2.2.2> route-map SET-MED out

route-map SET-LP permit 10

match ip prefix-list New2-x.x.xblock<<<<<<<<<<<<<<<<<

Set local-preference 250

route-map SET-LP permit 20

Set local-preference 200

route-map SET-MED

set metric 100

ip prefix-list New2-x.x.xblock permit 216.c.c.0/19

Here ,outgoing traffic follows local prefernce and incoming traffic comes following MED. Segregate the incoming routes in such a way that half of the routes(New1-x.x.xblock) have LP-250 and not in the block has LP 200

The opposite is to be configured in the Router2. For outgoing routes if we can know the exact routes getting from provider we can play with Med. Else default MED is ok.

The concept is simple, please revert back if find complications

Continued from an OLd Posting-BGP advertise problem-Ques.

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

Thanks for getting back to me. Thanks for the Template.

Using MED, wouldn't this be communicated to the provider? or its local and we can use it any time we need it?

did you find any problems in the cofiuration that I posted and of why traffic choosed to go out using one of the links only?

Also, can you please clarify what you call traffic inbound and trrafic out bound?

I assume any trffic going out of my routers to the providers are outbound and any traffic received by our routers from the providers as "inbound", did you assume the same thing?

i only have 4 days before I can bring up pthese routers again. do you think this will do the trick?

how about spliting my blocks? wouldn't that caused half of the blocks not be advertised when a link or a router is down?

Please advise,

Regards,

Masood

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

By the way, we have requested default or partial routes to be received form the provider. would this changes the situtaion/template?

that is why I had the 0/0 in the configuration on both the routers.

let's assume, partial routes to be received please.

Regards,

Masood

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

First of all, sorry for replying a bit late

As per the template we can only influence the outgoing traffic(Via LP)For this case, the traffic is distributed partially on the primary and the back up, hence outgoing traffic is perfect. But for incoming traffic, if we need to load balance its very dufficult(Probably Service Provider needs to do configuration on the router). Return traffic or incoming traffic will always flow via Primary and if Primary goes down, changes to Back up link(via Med).

If we require the incoming traffic is manipulated as load balancing effectively, we will ask Service provider to set commutinities during the entry point of the Service provider network and set LP accordingly for subnets on the exit point of the Service Provider network ie(PE connected to the Primary and Backup). This is only done on the Service provider router.

For any clarifications please revert back

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

The partial and default routes from Service provider does not change the configuration required in the CE

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

would you be able to please tell me why the configuration I posted didn't advertise route/blocks through the two routers and only through one router out to one proivider?

This is what I am trying to solve!

Please advise,

Regards,

Masood

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

Thanks very much. To me you are using MPLS terminology! correct!

I am only using BGP to speak to two different providers and when I turned up the network last week, I noticed that traffic only flows out through one of the routers althogh I had advertised my blocks correctly!

it seems that the load sharing isn't taking place based on the BGP configuratuion that I had posted and this is what makes me worry since Ihave to bring this network up again this coming Saturday night.

Also, I will only receive 0/0 from the provoders so its the outgoing traffic from my routers to the provides are not taking place the way I want it based on the IP Prefixes advertisingf our blocks!??

Any advise on nteh load-shring part will be gratetly appreciated.

Regards,

Masood

Community Member

Re: Continued from an OLd Posting-BGP advertise problem-Ques.

Hi Masood ,

Although I am not clear about your scenerio completely like how you are contolling traffic on from LAN to 2 Routers (LAN) . R u using any HSRP or what ?? See here 2 flows are involved :

1) Outgoing traffic (Upload)

2) Incoming traffic (DownLoad)

2)

Lets First talk about Download tarffic first . ITs always critical . I am considering that your requirement is for Internet (not for Private MPLS VPN).

Here simple way is to use AS Prepending to influence all incoming traffic. This will provdie Load balaning as well as Redundancy on prefix basis. & also you dont have to rely on service provider.

1) Upload traffic , As I told I am not sure how is traffic is reaching from LAN to your's 2 CE. R u using any load balancer or 2 different HSRP Groups ?? To me both CEs are getting default route from Service provider. so it totally depend on how traffic is coming from LAN to router. By using HSRP / Routing Protocol/ Load balancer this can be influence.

I hope it will give some help ..

Let me know incase of any query ....

ALL d BEST !

Pradeep M.

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