Re: HSRP and BGP [7:59735]
In your scenario advertising same block over both links to your provider will not help in load sharing. Redundancy is acheived but not sharing because your ISP will receive two advertisments to the same block and BGP only chooses the best route. You can overcome this in many ways, for example you if you have a /22 block. Devide it into 8 /24 blocks. Start advertising 4 /24s through the 1st router, advertise the remaining /24s through the 2nd router. Like this you acheived load-balance as your ISP will receive 1/2 of the routes via one link and the rest through the other. You are not done yet as this will provide load-sharing but not redundancy. For example if Link1 fails this means that 1/2 of your blocks will not be advertised and will stop receiving traffic for them. To avoid this, advertise through both routers an aggregate route for the whole /22. Like this your ISP will always use the more specific route and in a way balance the traffic over both links. When one of the links/routers fail, your ISP will use the aggregate route advertised from your other router to route all the traffic back to you. Another way, is to ask your provider to accept not just 1 route for the /24 but accept both by setting the maximum accepted routes to 2 instead to 1. 1 is the default and ISPs normally don't accept changing this default value. HTH, Yasser From: Ivan Yip Hi All, Thanks all your response. Now two routers adverise same block /24 to the isp. I found that they are 'load shared' in this sense. Only 1 link is the active for Inbound. For example, if I download files from outside, inbound is using say link1 and link2 is idle and no packet coming in. Some time later, I ftp again and this time is using link2 and link1 is idle. Is it normal? TIA. misconduct and Nondisclosure violations to [EMAIL PROTECTED] Protect your PC - Click here for McAfee.com VirusScan Online Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59753t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HSRP and BGP [7:59735]
While several of us have mentioned splitting up the netblocks that you advertise to your ISP would help spread the usage across the T1's there is something to keep in mind. If there is only 1 or so hosts that are most often the destination for traffic inbound to your site, you are still going to get more utilization across the link that advertises the network that contains that particular host/s. I mention this because I've had clients in the past split netblock assignments in an effort to get better utilization of their multiple T1 setups. But we've often found that they have 1 host providing more service than the others, that particular network will see more traffic, hence, that particular link seeing more utilization. There can be a need to be very granular about how you advertise networks and about how you have your network set up. You may have to play with moving hosts around on different netblocks if you are truly looking to get something near even traffic on each T1. You can use your interface stats to routinely check load, or better, use something like MRTG that will poll your interfaces and graph utilization over longer periods of time. Sorry if this is long winded, but you need to keep in mind what your trying to do. How to best use the resources you have and perhaps most importantly, to know how to measure it accurately to see if you've achieved the results you were looking for. -chris - Original Message - From: YASSER ALY To: Sent: Monday, December 23, 2002 11:43 AM Subject: Re: HSRP and BGP [7:59735] In your scenario advertising same block over both links to your provider will not help in load sharing. Redundancy is acheived but not sharing because your ISP will receive two advertisments to the same block and BGP only chooses the best route. You can overcome this in many ways, for example you if you have a /22 block. Devide it into 8 /24 blocks. Start advertising 4 /24s through the 1st router, advertise the remaining /24s through the 2nd router. Like this you acheived load-balance as your ISP will receive 1/2 of the routes via one link and the rest through the other. You are not done yet as this will provide load-sharing but not redundancy. For example if Link1 fails this means that 1/2 of your blocks will not be advertised and will stop receiving traffic for them. To avoid this, advertise through both routers an aggregate route for the whole /22. Like this your ISP will always use the more specific route and in a way balance the traffic over both links. When one of the links/routers fail, your ISP will use the aggregate route advertised from your other router to route all the traffic back to you. Another way, is to ask your provider to accept not just 1 route for the /24 but accept both by setting the maximum accepted routes to 2 instead to 1. 1 is the default and ISPs normally don't accept changing this default value. HTH, Yasser From: Ivan Yip Hi All, Thanks all your response. Now two routers adverise same block /24 to the isp. I found that they are 'load shared' in this sense. Only 1 link is the active for Inbound. For example, if I download files from outside, inbound is using say link1 and link2 is idle and no packet coming in. Some time later, I ftp again and this time is using link2 and link1 is idle. Is it normal? TIA. misconduct and Nondisclosure violations to [EMAIL PROTECTED] Protect your PC - Click here for McAfee.com VirusScan Online Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59759t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HSRP and BGP [7:59735]
Dear All, Thanks all useful information. Merry Christmas and Happy New Year!!! rgds, ivan Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59777t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
HSRP and BGP [7:59735]
Hi, I have 2 routers configured with HSRP and running BGP with single ISP. For outbound traffic, it will go through the Active HSRP router. How about Inbound traffic? Can the Inbound traffic be 'load shared'? (The ISP already make the same preference on our route advertised) Or the Inbound traffic can only route back to active router link? TIA. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59735t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HSRP and BGP [7:59735]
Usually if you want to distribute inbound traffic between two links with the SAME isp, you attach both of those links to the same router, create a loopback ip on that router, and have your provider peer with that loopback ip. Putting them on different routers will give you redundancy as opposed to load sharing. Brian - Original Message - From: Ivan Yip To: Sent: Sunday, December 22, 2002 6:18 PM Subject: HSRP and BGP [7:59735] Hi, I have 2 routers configured with HSRP and running BGP with single ISP. For outbound traffic, it will go through the Active HSRP router. How about Inbound traffic? Can the Inbound traffic be 'load shared'? (The ISP already make the same preference on our route advertised) Or the Inbound traffic can only route back to active router link? TIA. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59736t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HSRP and BGP [7:59735]
Hi, inbound traffic has nothing to do with HSRP.It all depends how your isp is routing back traffic through bgp.so it means u can load balance on the two links. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59737t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HSRP and BGP [7:59735]
Hi, inbound traffic has nothing to do with HSRP.It all depends how your isp is routing back traffic through bgp.so it means u can load balance on the two links. Ivan Yip wrote: Hi, I have 2 routers configured with HSRP and running BGP with single ISP. For outbound traffic, it will go through the Active HSRP router. How about Inbound traffic? Can the Inbound traffic be 'load shared'? (The ISP already make the same preference on our route advertised) Or the Inbound traffic can only route back to active router link? TIA. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59738t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HSRP and BGP [7:59735]
Hi, I have 2 routers configured with HSRP and running BGP with single ISP. For outbound traffic, it will go through the Active HSRP router. How about Inbound traffic? Can the Inbound traffic be 'load shared'? (The ISP already make the same preference on our route advertised) Or the Inbound traffic can only route back to active router link? You get back what you advertise out. So if you want some traffic to take one link and other traffic to take the other link, then you need to advertise it that way. Let's say you have a /24 netblock. You can advertise the first half of addresses (/25) out router A and the back half (/25) out router B. Then, take it a step further by also advertising the whole /24 block out both. This way, should one link fail, the other will pick up the traffic initially destined for the failed link. This based off of the longest-match rule. Please note - my example uses a /24 split into 2 /25s. Most providers won't accept (more specifically, won't advertise to their peers) any block smaller than a /24. There are some exceptions (such as having leased your netblock from that provider). Ask your provider what their policy is. Either way, work with your provider to get the advertisements setup correctly. This is the beauty of BGP. It has all the knobs you need for such requirements. HTH, -chris Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59739t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HSRP and BGP [7:59735]
Hi All, Thanks all your response. Now two routers adverise same block /24 to the isp. I found that they are 'load shared' in this sense. Only 1 link is the active for Inbound. For example, if I download files from outside, inbound is using say link1 and link2 is idle and no packet coming in. Some time later, I ftp again and this time is using link2 and link1 is idle. Is it normal? TIA. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59740t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HSRP and BGP [7:59735]
Ivan Yip wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Hi All, Thanks all your response. Now two routers adverise same block /24 to the isp. I found that they are 'load shared' in this sense. Only 1 link is the active for Inbound. For example, if I download files from outside, inbound is using say link1 and link2 is idle and no packet coming in. Some time later, I ftp again and this time is using link2 and link1 is idle. Is it normal? depends - per packet load sharing versus per conversation load sharing. with per packet load sharing set up correctly, each packet might take a different path. with per conversation load sharing, it is quite easy for this to happen. lets say that the router to microsoft.com is on your router's route cache for one link. any traffic to microsoft would take that one link, no matter how many other links to the internet you may have. later, you go to redhat.com. the route is not in the route cache, lookups are made, and the router chooses a different path. you really need to look at this in detail both on your side and with regards to what your ISP is doing. TIA. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=59741t=59735 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
