Using more than two L3 IPs on 2811

Unanswered Question

We have purchased 2811 with Advanced Security IOS and an extra HWIC-4ESW, 4 port ethernet interface card, in the hope they would be able to cater bring in multiple WAN links in the future, but as someone tells us, on a 2800 series, we can assign real IPs off two subnets ONLY to two physical ethernet interfaces, the other interfaces can form a VLAN of the same subnet or we will have to use SVI (virtual interfaces), to assign more than 2 real IPs.

Is this contention correct? Can I not define more than two IPs belonging to different IP subnets on my 2811 router in any way?

Please advise?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Jon Marshall Wed, 04/09/2008 - 23:53

Yes you need to use SVI's if you want to have more routed interfaces. The HWIC-4ESW is a layer 2 switch only. However there is nothing stopping you creating 4 vlans, 4 SVI's one for each vlan and then allocating each port into one of the vlans. That would give you 4 L3 SVI routed interfaces and 2 physical.


Jon Marshall Thu, 04/10/2008 - 02:57

No your'e not wrong in the sense that it supports 4 HWIC cards but it depends on the HWIC cards you purchase. The one you have could terminate a WAN link if the presentation was ethernet but not if it is ATM or serial for example.


Richard Burts Thu, 04/10/2008 - 04:37


It seems to me that we should differentiate what the router is capable of in general from what the particular router that you purchased and the particular card that you purchased. You mention: "that says 2811 supports 4 HWIC cards so I thought, 4 WAN Links are supported"

Certainly 4 WAN links are supported if you buy other types of HWIC cards.

The HWIC that you purchased provides a 4 port switch. If you want 4 separate addresses on it then Jon has told you how you can accomplish that with 4 SVIs. If you have 4 Ethernet connections then the card that you have should work ok. If you need 4 WAN connections that are not Ethernet then you need to purchase a different type of HWIC.



Richard Burts Sat, 04/19/2008 - 06:48


I have looked and I do not believe that there is an HWIC for the 2811 that supports fiber. I believe that you might have several options but all require some additional equipment. Perhaps you can purchase some fiber to copper converters and use those to interface to the HWIC. Or perhaps you can purchase some switch that supports fiber and connect it to the 2811.



Paolo Bevilacqua Sun, 04/20/2008 - 14:48

How many fiber circuits do you need ? You can place a simple 2960 switch to terminate fiber, asn multiple ethernet circuts and present them as vlan to the router over a single or multiple interface.

You can also check the 2821 and bigger, that can use an SFP module for direct fiber interface.

In any case, an ISR class router will not be able to process traffic at wire speed between fastethernet interfaces, so a lot also depednd by the intended application.


This Discussion