Kevin Dorrell, CCIE #20765

20 Feb 2008

IOS Gotcha : Frame Relay and PPP

Filed under: Frame Relay, PPP, WAN — Tags: , , — dorreke @ 20:00

frame-relay interface-dlci 304 ppp  

This is the first of a series of postings I intend to write covering some IOS “gotchas”: pitfalls for the unwary in the CLI.

Suppose you have configured the Virtual-Template, configured the Frame Relay subinterface, but you have forgotten to specify the PPP, so you have something like this:

interface Serial0/0.34 point-to-point 
 frame-relay interface-dlci 304 
 end

You then realize you mistake and try and add on the PPP stuff:

R3#conf t 
Enter configuration commands, one per line.  End with CNTL/Z. 
R3(config)#interface Serial0/0.34 point-to-point 
R3(config-subif)#frame-relay interface-dlci 304 ppp Virtual-Template1 
R3(config-fr-dlci)#end 
R3#

Has it taken it? No it hasn’t!

R3#show run int S0/0.34 
Building configuration... Current configuration : 80 bytes 
! 
interface Serial0/0.34 point-to-point 
 frame-relay interface-dlci 304 
end

If you want to add the PPP stuff, you have to remove the interface DLCI, and then put it back again with the PPP link:

R3#conf t 
Enter configuration commands, one per line.  End with CNTL/Z. 
R3(config)#interface Serial0/0.34 point-to-point 
R3(config-subif)#no frame-relay interface-dlci 304 
R3(config-subif)#frame-relay interface-dlci 304 ppp Virtual-Template1 
R3(config-fr-dlci)#end 
R3#

Now we have it:

R3#show run int S0/0.34 
Building configuration... Current configuration : 99 bytes 
! 
interface Serial0/0.34 point-to-point 
 frame-relay interface-dlci 304 ppp Virtual-Template1 
end

The moral of the story is to make no assumptions, and always look at your running configuration after you have configured it.

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1 Comment »

  1. […] One configuration “gotcha” caught me out.  I have tripped over so many “gotchas” in the past that I have decided to make a list of them (top rightunder “pages”) and write a small posting on each. […]

    Pingback by NMC Lab 8 « Kevin Dorrell’s CCIE Study Weblog — 21 Feb 2008 @ 23:06


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