Upgrading WAN do we still need ISR routers

[Nick Currie]

Hi there, apologies for what may be a dumb question - but I was just wondering if this may be possible.

We currently have a WAN where our remote sites are connecting using 4331 and 4321 ISR routers.

We use BGP for our routing protocol, with route maps and a prefix list to give preference where some networks are available on multiple WAN links.

For QOS  we are using NBAR2 for classification - with some custom entries and DSCP marking based on our class maps populated by nbar2 protocols.

This seems to be working pretty well, but we are in the process of centralization and we may be beefing some of our links up considerably to 500 mbit or 1 gbit in some cases.

According to the ISR throughput info i have found we would need to go to the 4431 for 500 Mbit - 1 Gbit sites and 4331 for the 100 Mbit sites..

At the same time as this we may be looking to refresh some of our old switching at these sites, currently ancient 3750's in a VSS. If we were to replace these stacks with the 9300 series catalyst routers - would we be able to perform the same QOS  / Routing functionality on those rather than purchasing another ISR as well?

We also have a couple of 4500 series chassis at our DC with SUP8 modules in them, would that also be able to handle a 1 gbit link and apply those same L3 functionalities on a routed WAN port?

[Leo Laohoo]

Do the routers handle NAT or not?

[Nick Currie]

No they don't perform any NAT at all.

[Joseph W. Doherty]

Generally, L3 switches are "feature poor" compared to ISRs. Leo touched on one such feature, NAT, but L3 switches have less capable QoS, many don't support tunnels, or tunnels with encryption, etc. It really depends on your needs. I.e. L3 switches might be just fine, or they may not be. BTW, when looking at switches, "MetroE" switches often offer a few additional features not found on "LAN" switches.

A 4500 sup8 can easily handle gig, or even 10g, capacity wise. Again, you may find it missing features found on an ISR.

The Catalyst 9300, at this time, is a bit of an unknown. It does whatever it does now, but with its newer ASICs, additional features may appear later. Ideally, see if you can discuss its roadmap with Cisco on a NDA basis.

[Nick Currie]

Thanks Joseph. Yes thats why I was asking about the QOS, would it support using NBAR2 to put specific protocols into classmaps and apply DSCP markings that way with a shape average parent policy, as that is how we are doing it currently and that will suffice.

[Joseph W. Doherty · Accepted solution]

Cisco L3 switches (especially "LAN" L3 switches) don't often support shapers or NBAR.