Adding new frame relay to 2611

[johannv]

Currently have a frame relay circuit on an end point terminating into a 2611.

interface Serial0/0

.....

interface Serial0/0.101 point-to-point

ip address 192.168.101.6 255.255.255.252

frame-relay interface-dlci 101

!

If i add 2 new frame drops then I need to add 2 more sub-interfaces(Question)

interface Serial0/0.102 point-to-point

ip address 192.168.101.7 255.255.255.252

frame-relay interface-dlci 30

!

interface Serial0/0.103 point-to-point

ip address 192.168.101.8 255.255.255.252

frame-relay interface-dlci 31

!

Is my assumption correct? Please advise I lost my Cisco consultant and our company is to cheap to have a service contract. Thanks

[Richard Burts]

Johann

Your assumptions are essentially correct. If you add two Frame Relay PVCs you would probably want to add two additional point to point subinterfaces (there are actually some other choices, but the point to point subinteface is usually the best option).

Each subinterface needs a unique number as its identifier, it needs an IP address, and it needs the DLCI assigned. Many of us will configure the subinterface so that the subinterface number is the same as the DLCI number (so it might be serial0/0.30 and serial0/0.31 but serial0/0.102 and serial0/0.103 would not be incorrect.

One problem with your example is the IP addresses that you included. If 192.168.101.6 is one of the addresses, 192.168.101.7 is in the same subnet, and 192.168.101.8 is a subnet address. You would need addresses like 192.168.101.6, 192.168.101.10, and 192.168.101.14. (And the addresses you use on your end of the connection need to be coordinated with the addresses used on the other end of the connection by whoever is configuring those routers)

HTH

Rick

[johannv]

Rick

Thanks for the reply. Using the DLCI number scheme makes sense.

Not sure about the IP address concern. The 2611 (OPTGS Router) in used for the current Frame Relay has a serial interface for the existing frame 192.168.101.6 and one ethernet interface 192.168.20.2. The 1721 for the existing frame PVC has a sub interface of 192.168.101.5 On OPTGS the ethernet interface goes into another 2611 as 192.168.20.1 and everything is routed to 192.168.20.1 This router (OPTCOLO) has a gateway interface 192.168.12.254 for our private .12 network, all of our unix/windows production servers at our colo. This router also has a point to point T1 with our office location S0/1 192.168.101.1, the other end of the T1 has an address of 192.168.101.2 on a 2611 here at the office. I was assuming to use .7 an .8 on the 101 network as the next available addresses. Please tell me what am I missing, again thank you kindly for your time.

[Richard Burts]

Johann

The concept that you are missing is the concept of subnet. A subnet is a group of addresses for machines that are on a common network segment. Your first Frame Relay is a segment and has its own subnet, your Ethernet is a segment and has its own subnet. When you add an additional Frame Relay connection on its own subinterface it is a segment and needs its own subnet.

Determining what addresses belong in a subnet is done by the IP address and the subnet mask. Your existing Frame Relay is 192.168.101.6 with a mask of 255.255.255.252. This indicates that the subnet begins at 192.168.101.4. The subnet includes addresses .5 and .6 and .7 is the broadcast address of that subnet. When you add a new Frame Relay connection it will need its own subnet with its own addresses that do not overlap with other subnets. As I said in my previous post it would make sense to use addresses .10 and .14 for the two new Frame Relay connections - assuming that those subnets are not already used somewhere in the network.

HTH

Rick