# Cisco 1841, Bridge T1 WAN to hosts with public IPs?

We currently have a Samsung router given to us by Covad. It is configured like this:

              PPPoFR T1 WAN (samsung router)
gateway
|
|
__________________________________________________________________
|                                                              |
|                                                              |
ethernet port(samsung router)              ethernet port(samsung router)
|                                                              |
|                                                              |
separate firewall/NAT                                separate firewall/NAT
|                                                              |
server LAN                                             VOIP LAN


So the Samsung router is routing the T1 WAN to the two firewalls, each firewall has its own public address in the same network as the gateway.

I desperately need to replicate this with a Cisco 1841 so I can get QOS going for the VOIP side. I have looked at IRB, but that mentions VLANs which seemed confusing when all of the hosts that will connect to the router have public IPs.

So how do I configure fe0/0 and fe0/1 to let their connected hosts with public IPs (x.x.x.50 and x.x.x.51) get to serial0/0/0(T1 WAN x.x.x.49)?

Thanks.

• You can use bridging on the router, but I don't see how that will help you with QoS. Bridging doesn't look into the layer-3 frame for the DSCP markings. IRB with a BVI would be what you need. – Ron Maupin Jan 17 '16 at 20:26
• Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 7 '17 at 18:04

In the Samsung (ibg1000???), the two ethernet ports form a switch:

interface ethernet 0/0
no keepalive
switchport
bridge-group 1
switchport mode access
qos
exit qos
no flowcontrol
exit ethernet
interface ethernet 0/1
no keepalive
switchport
bridge-group 1
switchport mode access
qos
exit qos
no flowcontrol
exit ethernet


In the 1841, the two ethernet ports are independent routed interfaces. You can simulate a switch by bridging the two ethernet ports, but I would not recommend it. Buy an external switch.

I think your best bet would be to put the Cisco router inside the firewall. You can mark the traffic on your switch(es), and queue it on the Cisco router interface to the firewall.

While it is a good idea to separate the VoIP traffic from the regular data traffic, you can do that with VLANs or with separate interfaces into the Cisco router. It doesn't matter if the traffic merges before or after the firewall since the queuing will will happen as it leaves the router, and that can happen before the firewall, too.

Your QoS policies will not be honored on the Internet, so all you can do is queuing on the exit interface.