Hank Nussbacher <HANK@VM.BIU.AC.IL> (05/28/91)
>Subject: Load Balancing between Equal Cost Routes > >If two serial links terminate at a the same cisco router at one end and to >the same node at the other end, will a cisco router recognise that there >are multiple equal cost routes to that node, and places beyond? >Can it be made to distribute transmitted packets between the two links? >What algorithm does it use? >Is any inter-router protocol required to be supported by the other node? > >Protocols of interest are PPP, TCP/IP, etc. It all depends what you are routing and also whether you are bridging. If you are routing TCPIP traffic it depends on what routing protocol is being used. RIP will not load balance, but IGRP will do a reasonable job of balancing the load on the two lines. If you are routing DECNET via Phase IV you will not be using one line at all and it will be more or less a hot standby. If the cost is the same on both lines the DECNET routing protocol will still only use one line. Phase V will load balance between the two lines. If you are bridging, then the cisco splits the load based on Ethernet addresses. It assigns some Ethernet addresses to one line and some to another line. This does a reasonable job of utilizing both lines. But if you have only one Ethernet station at the end of your two lines then the cisco will only utilize one of the two lines since it can't split the load among more Ethernet addresses. > >Thanks, >-Tim. Hank Nussbacher Israel
timr@labtam.labtam.oz (Tim Roper) (05/29/91)
In article <35406@boulder.Colorado.EDU>, HANK@VM.BIU.AC.IL (Hank Nussbacher) writes: > >Subject: Load Balancing between Equal Cost Routes > > > >If two serial links terminate at a the same cisco router at one end and to > >the same node at the other end, will a cisco router recognise that there > >are multiple equal cost routes to that node, and places beyond? > >... > > It all depends what you are routing and also whether you are bridging. > If you are routing TCPIP traffic it depends on what routing protocol > is being used. RIP will not load balance, but IGRP will do a reasonable > job of balancing the load on the two lines. If you are routing > DECNET via Phase IV you will not be using one line at all and it will > ... We are routing TCP/IP only and not bridging. Can anyone recommend sources of the specification of IGRP and/or sample implementations? Thanks, -Tim.
ferriby@perot.com (John Ferriby) (05/30/91)
In article <10613@labtam.labtam.oz>, timr@labtam.labtam.oz (Tim Roper) writes: > In article <35406@boulder.Colorado.EDU>, HANK@VM.BIU.AC.IL (Hank Nussbacher) writes: >> >Subject: Load Balancing between Equal Cost Routes >> > >> >If two serial links terminate at a the same cisco router at one end and to >> >the same node at the other end, will a cisco router recognise that there >> >are multiple equal cost routes to that node, and places beyond? >> >... >> >> It all depends what you are routing and also whether you are bridging. >> If you are routing TCPIP traffic it depends on what routing protocol >> is being used. RIP will not load balance, but IGRP will do a reasonable >> job of balancing the load on the two lines. If you are routing >> DECNET via Phase IV you will not be using one line at all and it will >> ... Just to clear up a common misconception... Unlike what the cisco documentation suggests, (by calling it Phase IV) the gateway software [8.2(3)] does in fact support path splitting. (This function falls under the DEC afterthought, Phase IV+, which among other things supports path splitting.) The configuration commands are 'decnet path-split-mode' and 'decnet max-paths'. I've found that the 'max-paths' tends to get folks who are experimenting with this -- it is defaulted to a value of 1 in both the DEC and cisco implementations. Intuitively, a value of 1 turns path splitting off. Also make sure that all routers involved are "symetrically configured" or your load will split in one direction but not the other or do some even weirder stuff if you have a mesh topology or more than 3 paths. Also of note, the the 'path-split-mode' value 'interim' supports those cases where a Phase IV router needs to talk to a Phase IV+ router, but I expect that is a relatively rare condition. > > We are routing TCP/IP only and not bridging. > > Can anyone recommend sources of the specification of IGRP and/or sample > implementations? > > Thanks, > -Tim. -- John Ferriby Perot Systems Corporation Telephone: +1-313-641-3660 4555 Corporate Drive Internet: ferriby@perot.com Troy, MI 48098-6353 UUCP: {uunet,decwrl,sun,umich}!perot!ferriby
dug@kd4nc.UUCP (Doug Drye KD4NC) (05/30/91)
timr@labtam.labtam.oz (Tim Roper) writes: >Can anyone recommend sources of the specification of IGRP and/or sample >implementations? Chuck Hedrick's paper on IGRP is available in postscript format at ftp.cisco.com via anonymous ftp. Fetch the README file for what is available there.. Doug -- Doug Drye KD4NC
eden@fallout.uucp (Robert Eden) (05/30/91)
HANK@VM.BIU.AC.IL (Hank Nussbacher) writes: > If you are routing > DECNET via Phase IV you will not be using one line at all and it will > be more or less a hot standby. If the cost is the same on both lines > the DECNET routing protocol will still only use one line. Phase V will > load balance between the two lines. PHASE IV+ shipped with VMS 5.0 and some of the new routers support equal cost balancing. It is off by default and must be turned on with the PATH_SPLIT exec parameter. I'm not sure if the CISCO DECNET implementation supports this. ------------------------------------------------------------------------- Robert Eden 817-897-0491 EDEN@fallout.uucp Commanche Peak Steam Electric Station Glen Rose, TX ^^^^^^^^^^^^^^^^^^^^^ politicese for a nuke plant -------------------------------------------------------------------------