Cisco 3845 & Ethernet Hand-off from ISP

[bryan.lofland]

I am switching to a single Ethernet hand-off from my ISP which currently gives me 4 T1 lines.  I have a Cisco 3845 router that services the current T1s.  My question is since my ISP is giving me just a single Ethernet hand-off going forward can I connect it directly to the internal NICs on the 3845 or do I have buy some other HWIC?  I will be running a 100Mbps connection over the hand-off and the NICs are Gigabit NICs.  I will not be doing anything fancy over this, just simply a couple of routes in the routing table.  No VPN, no firewalling, etc.  The specs state that the 3845 is only for up to a T3 speeds but I am not sure if that is for the HWIC interfaces or for the whole thing in general?

[Collin Clark · Accepted solution]

Yes you can plug the ethernet hand-off directly to the chassis gigabit interface and no additional hardware is required. The 3845 chassis can handle 256Mbps.

UPDATE: Sorry I was reading the wrong line (if you saw my post before I edited it).

[bryan.lofland]

Collin,

Thanks for the quick answer.  I figured so as it didn't make much sense that Cisco would not be able to purely route packets at 100Mbps on really almost any modern equipment.

Thanks,

Bryan

[Joseph W. Doherty]

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Posting

Just a point of clarification, the 256 Mbps Collin noted would need to be halved if dealing with duplex traffic, i.e. a 3845 doesn't have a large reserve for 100 Mbps duplex.  However, that's also for minimum sized packets and there's less overhead routing Ethernet to Ethernet, so you'll probably be fine but be careful about making assumptions about the performance of "modern" Cisco equipment.