RE: Per-destination load balancing [7:72944]
Tim Champion wrote: > > Could someone please confirm the following to be true (taken > from CCO): > > "Per-destination load balancing allows the router to distribute > packets > based on the destination address, and uses multiple paths to > achieve load > sharing. Packets for a given source-destination host pair are > guaranteed to > take the same path, even if multiple paths are available. For > example, given > two paths to the same network, all packets for destination1 on > that network > go over the first path, all packets for destination2 on that > network go over > the second path, and so on. Per-destination load balancing is > enabled by > default when you start the router, and is the preferred load > balancing for > most situations." > > It was my understanding that per-destination load balancing was > based on the > destination address only and not on the source/destination pair. > > If someone could clarify it would be much appreciated. > > Cheers > Tim This probably depends on the switching mechanism in place. Fast switching, as I recall, simply caches the outgoing interface for any given destination so it's relying on the destination information only. CEF uses both the source and destination. Multiple sources trying to reach the same destination might not use the same outgoing interface. John Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=72962&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Per-destination load balancing [7:72944]
Packets for a given source-destination pair are a subset of packets for a given destination. It's true that with per-destination load balancing, all packets for a destination go out the same interface. Thus, it is true that all packets for a given source-destination pair go out the same interface. But I doubt the router acutally looks at the source address with basic packet forwarding, so the tech writer who wrote the paragraph below probably should not have embellished it with that addition, unless it was somehow relevant to some other part of the discussion. It's hard to tell without seeing the entire context. Hope that makes sense. Priscilla Tim Champion wrote: > > Could someone please confirm the following to be true (taken > from CCO): > > "Per-destination load balancing allows the router to distribute > packets > based on the destination address, and uses multiple paths to > achieve load > sharing. Packets for a given source-destination host pair are > guaranteed to > take the same path, even if multiple paths are available. For > example, given > two paths to the same network, all packets for destination1 on > that network > go over the first path, all packets for destination2 on that > network go over > the second path, and so on. Per-destination load balancing is > enabled by > default when you start the router, and is the preferred load > balancing for > most situations." > > It was my understanding that per-destination load balancing was > based on the > destination address only and not on the source/destination pair. > > > > If someone could clarify it would be much appreciated. > > > > Cheers > > > > Tim > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=72954&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Per-destination load balancing [7:72944]
If there are multiple levels of Heaven and our final destination has been predetermined in order to equalize the number of people in each level, would this be considered pre-destination load-balancing? >>> Priscilla Oppenheimer 7/24/03 1:24:34 PM >>> Packets for a given source-destination pair are a subset of packets for a given destination. It's true that with per-destination load balancing, all packets for a destination go out the same interface. Thus, it is true that all packets for a given source-destination pair go out the same interface. But I doubt the router acutally looks at the source address with basic packet forwarding, so the tech writer who wrote the paragraph below probably should not have embellished it with that addition, unless it was somehow relevant to some other part of the discussion. It's hard to tell without seeing the entire context. Hope that makes sense. Priscilla Tim Champion wrote: > > Could someone please confirm the following to be true (taken > from CCO): > > "Per-destination load balancing allows the router to distribute > packets > based on the destination address, and uses multiple paths to > achieve load > sharing. Packets for a given source-destination host pair are > guaranteed to > take the same path, even if multiple paths are available. For > example, given > two paths to the same network, all packets for destination1 on > that network > go over the first path, all packets for destination2 on that > network go over > the second path, and so on. Per-destination load balancing is > enabled by > default when you start the router, and is the preferred load > balancing for > most situations." > > It was my understanding that per-destination load balancing was > based on the > destination address only and not on the source/destination pair. > > > > If someone could clarify it would be much appreciated. > > > > Cheers > > > > Tim Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=72970&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Per-destination load balancing [7:72944]
At 4:01 PM + 7/24/03, Tim Champion wrote: >Could someone please confirm the following to be true (taken from CCO): > >"Per-destination load balancing allows the router to distribute packets >based on the destination address, and uses multiple paths to achieve load >sharing. Packets for a given source-destination host pair are guaranteed to >take the same path, even if multiple paths are available. For example, given >two paths to the same network, all packets for destination1 on that network >go over the first path, all packets for destination2 on that network go over >the second path, and so on. Per-destination load balancing is enabled by >default when you start the router, and is the preferred load balancing for >most situations." > >It was my understanding that per-destination load balancing was based on the >destination address only and not on the source/destination pair. There are two distinct modes. Fast, silicon, autonomous and optimum switching are destination only. CEF is source/destination pair. I would consider CEF superior in just about any case I can think of, as long as the platform and IOS supports it. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=72996&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Per-destination load balancing [7:72944]
Thank you for your replies, think I've got it now. ""Tim Champion"" wrote in message news:[EMAIL PROTECTED] > Could someone please confirm the following to be true (taken from CCO): > > "Per-destination load balancing allows the router to distribute packets > based on the destination address, and uses multiple paths to achieve load > sharing. Packets for a given source-destination host pair are guaranteed to > take the same path, even if multiple paths are available. For example, given > two paths to the same network, all packets for destination1 on that network > go over the first path, all packets for destination2 on that network go over > the second path, and so on. Per-destination load balancing is enabled by > default when you start the router, and is the preferred load balancing for > most situations." > > It was my understanding that per-destination load balancing was based on the > destination address only and not on the source/destination pair. > > > > If someone could clarify it would be much appreciated. > > > > Cheers > > > > Tim Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=73009&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Per-destination load balancing [7:72944]
Here's some text from CCO regarding CEF and using source and destination IPs to map a packet to one of a set of load sharing links: Configuring Per-Destination Load Balancing Per-destination load balancing is enabled by default when you enable CEF. To use per-destination load balancing, you do not perform any additional tasks once you enable CEF. Per-destination load balancing allows the router to use multiple paths to achieve load sharing. Packets for a given source-destination host pair are guaranteed to take the same path, even if multiple paths are available. Traffic destined for different pairs tend to take different paths. Per-destination load balancing is enabled by default when you enable CEF, and is the load balancing method of choice for most situations. The URL for the above is (watch wrap): http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6ca.html#1000956 John Neiberger wrote: > > Priscilla Oppenheimer wrote: > > > > John Neiberger wrote: > > > > > > Tim Champion wrote: > > > > > > > > Could someone please confirm the following to be true > (taken > > > > from CCO): > > > > > > > > "Per-destination load balancing allows the router to > > > distribute > > > > packets > > > > based on the destination address, and uses multiple paths > to > > > > achieve load > > > > sharing. Packets for a given source-destination host pair > > are > > > > guaranteed to > > > > take the same path, even if multiple paths are available. > > For > > > > example, given > > > > two paths to the same network, all packets for > destination1 > > on > > > > that network > > > > go over the first path, all packets for destination2 on > that > > > > network go over > > > > the second path, and so on. Per-destination load balancing > > is > > > > enabled by > > > > default when you start the router, and is the preferred > load > > > > balancing for > > > > most situations." > > > > > > > > It was my understanding that per-destination load > balancing > > > was > > > > based on the > > > > destination address only and not on the source/destination > > > pair. > > > > > > > > If someone could clarify it would be much appreciated. > > > > > > > > Cheers > > > > Tim > > > > > > This probably depends on the switching mechanism in place. > > Fast > > > switching, as I recall, simply caches the outgoing interface > > > for any given destination so it's relying on the destination > > > information only. > > > > Yes, fast-switching caches the outgoing interface for a > > destination. All packets to a particular destination go out > the > > same interface. CEF works that way too if you use the default. > > > > > CEF uses both the source and destination. > > > > I don't think that is true? CEF doesn't look at source > > addresses. > > I just checked this on our 7513 running 12.2(17a). If you use > the command "show ip cef exact-route sourceip destinationip" > you'll see the cached exit interface. If you do this with > several source addresses going to the same destination when > there are multiple paths you'll see that they use different > exit interfaces. > > I wonder if the default behavior has changed as CEF has evolved? > > John > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=73026&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Per-destination load balancing [7:72944]
At 2:34 PM + 7/25/03, p b wrote: >Here's some text from CCO regarding CEF and using source >and destination IPs to map a packet to one of a set of >load sharing links: > >Configuring Per-Destination Load Balancing > >Per-destination load balancing is enabled by default when you enable CEF. To >use per-destination load balancing, you do not perform any additional tasks >once you enable CEF. > >Per-destination load balancing allows the router to use multiple paths to >achieve load sharing. Packets for a given source-destination host pair are >guaranteed to take the same path, even if multiple paths are available. >Traffic destined for different pairs tend to take different paths. >Per-destination load balancing is enabled by default when you enable CEF, >and is the load balancing method of choice for most situations. > >The URL for the above is (watch wrap): > >http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6ca.html#1000956 I think the problem here is the documentation author, not IOS. It seems fairly clear to me that said author doesn't understand the difference between traditional destination cache and source-destination hash. This hasn't been the first time strange things have happened. I remember that I looked at the original description of OSPF demand circuits and just blinked. First, I knew from the OSPF Working Group how they were supposed to work. Second, I knew the developer who wrote the code, and also wrote English very well. I sent him an email, and he responded he had absolutely no idea, either, what the documentation was trying to say. He observed his C code, even uncommented, was more readable. > > > >John Neiberger wrote: >> >> Priscilla Oppenheimer wrote: >> > >> > John Neiberger wrote: >> > > >> > > Tim Champion wrote: >> > > > >> > > > Could someone please confirm the following to be true >> (taken >> > > > from CCO): >> > > > >> > > > "Per-destination load balancing allows the router to >> > > distribute >> > > > packets >> > > > based on the destination address, and uses multiple paths >> to >> > > > achieve load >> > > > sharing. Packets for a given source-destination host pair >> > are >> > > > guaranteed to >> > > > take the same path, even if multiple paths are available. >> > For >> > > > example, given >> > > > two paths to the same network, all packets for >> destination1 >> > on >> > > > that network >> > > > go over the first path, all packets for destination2 on >> that >> > > > network go over >> > > > the second path, and so on. Per-destination load balancing >> > is >> > > > enabled by >> > > > default when you start the router, and is the preferred >> load >> > > > balancing for >> > > > most situations." >> > > > >> > > > It was my understanding that per-destination load >> balancing >> > > was >> > > > based on the >> > > > destination address only and not on the source/destination >> > > pair. >> > > > >> > > > If someone could clarify it would be much appreciated. >> > > > >> > > > Cheers >> > > > Tim >> > > >> > > This probably depends on the switching mechanism in place. >> > Fast >> > > switching, as I recall, simply caches the outgoing interface >> > > for any given destination so it's relying on the destination >> > > information only. >> > >> > Yes, fast-switching caches the outgoing interface for a >> > destination. All packets to a particular destination go out >> the >> > same interface. CEF works that way too if you use the default. >> > >> > > CEF uses both the source and destination. >> > >> > I don't think that is true? CEF doesn't look at source >> > addresses. >> >> I just checked this on our 7513 running 12.2(17a). If you use >> the command "show ip cef exact-route sourceip destinationip" >> you'll see the cached exit interface. If you do this with >> several source addresses going to the same destination when >> there are multiple paths you'll see that they use different >> exit interfaces. >> >> I wonder if the default behavior has changed as CEF has evolved? > > >> John Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=73031&t=72944 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
