[c-nsp] Design Q

[Bruce Pinsky]

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info at beprojects.com wrote:
| I've got a design question that I am not sure about and was wondering if
| anybody has any insight.
|
| My intention is to have two separate Internet routers running eBGP to
| two separate upstreams and then iBGP to each other.  On the LAN side,
| they will each have their own IP, say .2 and .3 and share a HSRP
| address, say .1.  If I'm on the LAN, my DG is .1.  If I try to go to
| some random Internet address, I will go to .1 and we'll say that right
| now, that is router A.  If the address is best reached through it, it
| will forward the packet.  If it is best reached through B, which it
| learns via iBGP, it will send an ICMP redirect, assuming they are
| enabled, and tell me to go to .3 instead, which will forward the packet.
|   So on my pc, I will build a routing table as I move along.
|
| The question is, what do I do if I want to create 4-5 VLAN's.  Say I
| have a layer3 switch like a 3750.  My initial thought would be to make
| it the DG for each vlan and it would have a default route of .1.
| However every time it gets a redirect, it will add it to it's routing
| table, right?  Now if one of the machines on one of the vlan's is a dns
| server or web server, theoretically, there could be thousands on
| different destinations, in which case the L3 switch will have thousands
| of routing entries and we all know that a lower end switch like the 3750
| does not have enough memory to hold 100,000 routes.
|
| Am I better off setting up the links to the routers as trunks and using
| sub interfaces?  Or am I way off in my description above?  Or is there
| some other option?
|

Take a look at the Gateway Load Balancing Protocol (GLBP) whitepaper at
http://www.cisco.com/en/US/partner/tech/tk869/tk769/technologies_white_paper0900aecd801790a3.shtml

It describes several techniques and introduces the feature as well.

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bep

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