At 12:18 PM +0000 2/13/03, DeVoe, Charles (PKI) wrote: >There are 2 7200 routers that connect to different providers. Traffic ends >up where it is supposed to. The problem is that we have intermittent slow >response times and some applications that don't work properly over the >internet. My suspicions are that some of the traffic is returning over the >smaller 512K line and that is causing congestion.
With two providers, it would be perfectly normal to see 30 percent or more of packets to go out one provider and come back on the other. This is due to the reality that a distant AS may see the path through the second provider as better from its perspective. There's no knob in BGP telling the receiver that it has to send on the reverse route followed by arriving packets. Use a default to the T3 provider, but set up a second, less preferred default to the 512K provider. You might want to use conditional advertisement so the second ISP will not even see your routes, although that may result in a delay during cutover. Prepend your AS at least 6 times if you do advertise continuously to the second provider. > >-----Original Message----- >From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] >Sent: Wednesday, February 12, 2003 5:29 PM >To: [EMAIL PROTECTED] >Subject: RE: Internet Connections [7:62863] > > >I think we need more info. Questions below... > >DeVoe, Charles (PKI) wrote: >> >> I have a class B network subnetted using a 21 bit mask. This >> network has 2 >> connections to the internet, 1 is by a T3 the other is a 512K >> T1. Each >> connection to the internet comes out of a subnet, goes through >> a firewall, >> and then through a Cisco 7200 router. We have static routes in >> place to >> assure that the returning packets go to the proper firewall. I >> don't know >> for sure if the routers connecting to the internet are running >> BGP or some >> thing else. We have seen packets go out one interface and >> return on the >> other. > >One interface of what? The 7200? Does the 7200 connect to multiple border >routers? Can you tell us more about that part of the topology? > >> I suspect that something is not right with the border >> routers. Any >> thoughts or suggestions? > >It's very difficult to control how traffic comes back into your network over >the Internet. Entire books by Berkowitz, etc. have been written on this >topic. > >But it's not necessarily a problem. If the traffic all ends up at the 7200 >and the 7200 is configured correctly with the static routes that you >mentioned, the traffic should end up at the right place. What problem are >you trying to solve? > >By the way, John makes a really good point about pinhole congestion. See his >post too. Thanks. > >Priscilla Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=62968&t=62863 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
