Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Community Member

Aggregating Multiple T1's

We recently added an additonal T1 to our 2621 router. Both T1's are point-to-point to the same ISP. How do you config these two T1 interfaces to aggregate or load-balance our outbound internet traffic? Thanks in advance for any help

Wayne

7 REPLIES
Silver

Re: Aggregating Multiple T1's

If the T1's connect to the same router at the ISP then you can ask your ISP about doing MultiLink PPP with you (MPPP).

http://www.cisco.com/warp/public/793/access_dial/pppmultilink.html

Here the routers will treat the two T1's as a single 3mbps pipe by splitting up the traffic packet by packet at Layer 2 (PPP).

You can also do equal cost IP load balancing by configuring two default routes on your router that point to the each of the ISP's routers. Here you should ask the ISP to use equal cost load balancing to your assigned address space so you can get inbound

traffic to load balance ... as this is the majority of traffic in a typical environment.

Regards,

Brad

Community Member

Re: Aggregating Multiple T1's

First, I would like to thank everyone for such a quick discussion thread. Via my ISP, the suggestion of 'equal cost IP load balancing with multiple default routes is the winner.

Thanks again,

Wayne

PS. If any of you are skiers and in the Park City area, look me up, I can provide complimentary ski passes.

Cisco Employee

Re: Aggregating Multiple T1's

ppp multilink is one solution.

You can also configure BGP between your loopback address and your isp loopback address with 2 static routes for the loopback(1 for each T1).

Community Member

Re: Aggregating Multiple T1's

Both methods look promising, but is there a best practice or least router impact for one or the other, ie Multilink vs BGP.

Thanks to both timely responses,

Wayne

Silver

Re: Aggregating Multiple T1's

Running BGP on a 2600 is certainly not recommended by Cisco nor myself.

The minimum router I would ever run BGP with is a 3640 fully loaded with DRAM (128mb). Mostly I recommend 7200's or better in BGP environments.

When connecting to only a single ISP there is no real point in running BGP anyway.

MPPP will provide the best load balancing but will utilize more cpu resources on your 2600.

Per-destination IP load balancing utilizing equal cost default routes will offer an easier configuration, and less cpu utilization.

However, given that most internet traffic is inbound, you should concern yourself with how your ISP is going to load balance to you.

MPPP is the best way to know that the ISP is load balancing to you, however your 2 T1's must be connected to the same router at the ISP.

The next step at this point is to contact the ISP to see what methods they are willing to configure with you.

Regards,

Brad

Re: Aggregating Multiple T1's

The notion that you really need a pumped-up router to run BGP is mostly overblown. Yes it is often advisable to have a good router to do your BGP, but it's not as necessary as a lot of people think. I've run BGP just fine on a 2500 with 8 MB RAM. The key is not to accept the entire BGP Internet route table and not to have lots of BGP peers, but regular enterprise networks have little reason to do either.

And even if you insist on accepting the entire BGP route table, it doesn't require THAT much memory. For example, 100,000 routes consumes only 71 MB of RAM, and 30,000 routes consumes less than 30 MB. BGP is resource-intensive, but not as resource-intensive as it is often made out to be.

http://www.cisco.com/warp/public/459/41.shtml

But yeah, the best way to do the load-balancing you need is to contact your provider.

Community Member

Re: Aggregating Multiple T1's

If taking only a few routes or a default route, running bgp on any router is less tazing then OSPF. BGP is a simple protocol.

212
Views
0
Helpful
7
Replies
CreatePlease to create content