Bridging With A Cisco 700 Series Router - Cisco 700 Series Configuration Manual

Bridging with a Cisco 700 Series Router

values for DMS-100 and NI1 switches: ISDN number, 4085551212; SPID 1,
408555121201; SPID 2, 408555121202. In this case the SPID is the 10-digit ISDN number
ending with a "01" for SPID 1 and a "02" for SPID 2.
Bridging with a Cisco 700 Series Router
This section describes how to bridge a Cisco 700 series router over an ISDN line to another
router. Bridging is used in cases where you do not need a lot of filtering to manage the
network. Basically, you are relying on the nodes on the LAN side of the router to determine
if a packet should be accepted or dropped. (If you turn routing on, you can filter the packets
on the WAN side, reducing your traffic on the LAN side.)
Note
the ISDN line helps optimize ISDN bandwidth by reducing traffic to the WAN.
Figure 3-1 illustrates an example of a remote Cisco 700 series router bridging to a router
called central at a central site.
Figure 3-1
You are going to establish a basic connection with another router, relying primarily on the
defaults. In this example configuration, a simple user-defined profile is created in your
Cisco 700 series router to bridge over an ISDN network to another router.
By default, the Cisco 700 series router automatically "learns" the MAC addresses that exist
locally and remotely across the WAN. The router stores the MAC addresses in a MAC
address table, so it knows if the unicast packets should remain on the LAN or forwarded
3-8 Cisco 700 Series Router Configuration Guide
Bridging over an ISDN line is not an efficient use of ISDN bandwidth. Routing over
Bridging Example
IP address 172.16.125.9
Subnet mask 255.255.0.0
Enterprise
CPA765
IP address 172.16.125.10
Subnet mask 255.255.0.0
San Jose
ISDN
Central
network