3750 and routing question.

we have a location mile away from the headquarter and until last week, it had a 100M wifi link, We just got another set of radios installed so there is a gig link (unused at the moment) now between the 2 buildings too.

all 4 radios terminate in a 3750 on either side and I am wondering if there is smarter way to use those links and not just channel bond them so they fail over for each other. I can push routing to those switches if need be but I am interested in using the 100M link just for critical traffic (remote desktop and telnet) and the gig link for commodity browsing and backups etc. so 100M link is really dedicated just for this one application that is housed at that building. Currently we can't back anything up over there because 100M link is nearly maxed out with just browser traffic.

anyone got any suggestion? I am happy to do some reading but just need some direction.


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Zerothly, I wouldn't bother with this unless it was proved nevessary.

Firstly be aware that the 3750 is a hardware router that can use software routing in some circumstances. The software routing performance will be rather poor.

I have no idea if PBR is handled in hardware on the 3750 but I doubt it very much.

I think you will need to use Policy Based Routing.

PBR is manually configured and can choose output interface or next-hop IP depending on arbitrary access-list matching.

If an interface is down it can fall back to routing via the routing table.

If your hardware does not force the router interface down on radio link loss you could perhaps use the SLA facility to force the interface down if the link is lost..

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Good luck.

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You do not want to channel bond links with widely different speeds.

Ganging Ethernet pipes together uses various ways to share traffic, but all the simple schemes (which is all that will work on a switch at GigE) assume all pipes have the same speed.

The net effect will be approx N x slowest link = 200 Mbps in your case.

whereas your fastest link is 1 G - so more complications and hassle for 1/5 the throughput.......

I can push routing to those switches

Run the 2 links as routed.

set the costs so your traffic "prefers" the GigE link, and use the

100M as a backup (note this assumes that when you lose something there is a fighting chance the GigE breaks but the 100M doesnt - if not, dont bother).

use QoS and possibly shaping to handle the special app - that way you can have different bandwidth setups, and rate limit how much it takes so other traffic gets serviced.

3750 has pretty good QoS, but not much buffering - but with higher speed links that doesnt matter so much. Tinker with the buffer pools at your peril....

it is also one of the few relatively cheap switches that can rate limit and also do QoS on the same port. So - if your GigE radio link is really say 400 Mbps, the switch can be set up to cope with that and still use QoS.....

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