Frame-relay subinterface help

Answered Question
Jun 20th, 2010
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I have a 2901 router that will be used to connect to an ISP and then our inside network will be connected through one of the Gig-ports on the 2901. I cannot figure out how to create a sub-interface on the 2901, it will not allow me to do it like I have done on other type of routers. The only way I can get it to configure anything at all is by:


interface Serial0/1/0:0

ip address x.x.x.x y.y.y.y

ip flow ingress

ip nat outside

ip virtual-reassembly

zone-member security out-zone

enacapsulation frame-relay IETF

frame-relay interface-dlci 500

frame-relay lmi-type ansi

crypto map SDM_CMAP_1



usually I would do it by:


interface Serial0/1/0

no ip address

encapsulation frame-relay IETF

ip route-cache flow

frame-relay lmi-type ansi

!

interface Serial0/1/0.500 point-to-point

frame-relay interface-dlci 500 IETF



Thanks for your help.

Correct Answer by Richard Burts about 6 years 9 months ago

It looks like the card in your router requires that you configure the T1 controller using the channel-group 0 command to create the serial interface. This produces a serial interface name like interface Serial0/1/0:0. Your comments seem to think that this creates a subinterface. But this is the name of the physical interface (the : 0 is a by-product of the channel group definition). Have you tried configuring interface Serial0/1/0:0.500 point-to-point?


HTH


Rick

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Correct Answer
Richard Burts Sun, 06/20/2010 - 12:37
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It looks like the card in your router requires that you configure the T1 controller using the channel-group 0 command to create the serial interface. This produces a serial interface name like interface Serial0/1/0:0. Your comments seem to think that this creates a subinterface. But this is the name of the physical interface (the : 0 is a by-product of the channel group definition). Have you tried configuring interface Serial0/1/0:0.500 point-to-point?


HTH


Rick

j.mccartney Sun, 06/20/2010 - 16:31
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The problem is that I cannot create a sub-interface at all from this point that's what my issue is. I have other 1841's that I have in the past that have had no problems creating a sub-interface. So my question is will the physical interface work with everything config'd on it (encap, lmi)?


Thanks for your help.

Richard Burts Sun, 06/20/2010 - 17:13
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You do not indicate whether you have actually attempted my suggestion to configure  interface Serial0/1/0:0.500 point-to-point. Can you clarify whether you have attempted this or not?


Assuming that your Frame Relay connection has only a single DLCI then I believe that your configuration with all parameters on the physical interface should work.


Note that the configuration with all parameters on the physical interface produces a multipoint interface while the subinterface that you suggest would be point to point. Some protocols (like OSPF) react differently to multipoint or point to point. Since you have not provided any information about your router environment, we are not able to offer advice about whether the difference between multipoint or point to point will make much difference.


HTH


Rick

j.mccartney Sun, 06/20/2010 - 17:55
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Hi again Rick,


Sorry I didn't clarify my last response. Yes,  I did try to create the subinterface as pt-pt to no avail, there were no commands even there to allow me to do a  "interface Serial0/1/0:0.500 point-to-point. Yes, we only have one DLCI too.


What we are doing is having a T1 installed at a remote site that is connected back to our HQ for a site-site VPN for data/phones. But the kicker is this is the first time we have done it with a 2901 in this topology. We have other sites that are utilizing MPLS VPN, some using Time Warner cable modem. Usually we have a T1 utilizing a site-site VPN (remote site ASA to our corp ASA) where we have a router connecting to an ASA and then to a switch for the local LAN.


I will try it again tomorrow when I get into my office and reply. The 2901 integrates the router/firewall in one device, so I'm trying some new things here. I do appreciate your help and suggestions.


John

j.mccartney Mon, 06/21/2010 - 06:00
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Hello Rick,


I was able to get it finally working with a sub-interface. I'm not sure what I was doing wrong before, but thanks for your help.


John

Richard Burts Mon, 06/21/2010 - 08:51
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John


I am glad that you got it working. Thanks for letting us know.


HTH


Rick

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