Nobody caught the typo! :-) In the priority list for ICMP (which I copied from the Telent example), I left in the keyword TCP. Obviously, it shouldn't be there. ICMP runs directly above IP and does not use TCP.
Priscilla Priscilla Oppenheimer wrote: > > Captian Lance wrote: > > > > You can use queuing to accomplish priority by protocol, > however > > ICMP and > > Telnet are two different protocols. Telnet, an application > > layer protocol, > > does not use ICMP. ICMP, a network layer protocol, is used > for > > message > > delivery, such as Echo requests and echo replies (PING). If > > you need > > additional help please send me an email. > > Please keep the conversations on the list so we all learn from > them! Thanks. :-) If you're worried that the conversation would > be too basic for the group, I would say in most cases, that's > not true. There's no such thing as a dumb question (or answer) > on a study group, IMHO, and lots of people need more info on > protocol behavior, since Cisco doesn't focus on that enough in > their learning materials. > > Telnet is indeed an application-layer protocol that runs above > TCP and IP. It's interactive and uses very short packets, with > each character you type in a single packet usually. The server > side may send bigger packets when it sends prompts (or screens > with TN3270), but the packets are still pretty small. > > With something like weighted-fair queuing (WFQ), Telnet would > be automatically prioritized, since short-packet flows are > prioritized automatically with WFQ. WFQ is on by default on > serial links with a speed of about 2 Mbps or less. > > If that doesn't help or doesn't apply to your situation, then > the easiest solution for prioritizing Telnet would be priority > queuing. The config would be something like: > > priority-list 1 protocol ip high tcp telnet > > int s0 > priority-group 1 > > This applies to traffic forwarded by the router, not to traffic > sent by the router. If your goal is to priorize Telnet access > to or from the router, I don't think you have to do anything. > It's pretty well prioritized anyway, as far as I know. > > Now, for ICMP. You could prioritize it also, although I would > wonder why you would want to do this. I think it would be a > mistake, since ICMP is used for pings. You could end up > prioritizing a ping scan, for example. And, in this case, if > you are trying to prioritize packets sent by the router, it > probably won't work. ICMP is purposely not prioritized by > routers. > > But if you want to prioritize ICMP packets forwarded by the > router, you could do priority queuing with: > > priority-list 1 protocol ip high tcp icmp > > int s0 > priority-group 1 > > One last caveat, though. ICMP is generally sent by the router, > not forwarded by the router. With the exception of ping (echo), > ICMP's main job is for a router to send back status and error > messages. > > The formatting for the following table from my book may get > screwed up, but I think you'll get the flavor of it. It lists > the ICMP message types to give you an idea of what ICMP is good > for: > > ICMP Types and Codes > Type Code Meaning > 0 0 Echo reply (ping reply) > 3 x Destination unreachable (generic category) > 3 0 Network unreachable > 3 1 Host unreachable > 3 2 Protocol unreachable > 3 3 Port unreachable > 3 4 Fragmentation was needed and the don't fragment (DF) bit > was set > 3 5 Source route failed > 3 13 Packet administratively prohibited > 4 0 Source quench* > 5 x Redirect (generic category) > 5 0 Redirect datagrams for the network > 5 1 Redirect datagrams for the host > 5 2 Redirect datagrams for the type of service and network > 5 3 Redirect datagrams for the type of service and the host > 8 0 Echo (ping) > 11 x Time exceeded (generic category) > 11 0 Time-to-live (TTL) exceeded > 11 1 Fragment reassembly time exceeded > 12 0 Parameter problem > > * Per RFC 1812, a router should not originate source quench > messages. A host may send source quench messages, however, per > RFC 1122. > > > Hope that helps! Send us another question once you figure out > what you really want to do. Thanks. > _______________________________ > > Priscilla Oppenheimer > www.troubleshootingnetworks.com > www.priscilla.com > > > > > Lance > > > > ""Johan Bornman"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > How do I prioritize ICMP (Telnet) traffic on a 1601, no > > routing protocol > > > involved. > > > > > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=61525&t=61453 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
