From: ccie2be (ccie2be@nyc.rr.com)
Date: Fri Jul 15 2005 - 13:10:44 GMT-3
Godswill,
What an excellent post !!!
I'm not sure if I ever heard those explanations before regarding "Deleted"
and "Inactive" or I just forgot exactly what they meant.
I knew in either case, I had a problem that needed to be fixed. Are those
explanations hiding somewhere on the Doc-CD?
And, are you 100% sure those meanings are correct? I don't have access to
equipment at the moment otherwise I would test that out myself.
TIA, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Godswill Oletu
Sent: Friday, July 15, 2005 11:08 AM
To: jellyboy; ccielab@groupstudy.com
Subject: Re: Back-to-Back FR
Jelly,
Let me see if I can give this a shot.................
To fully understand the reason, you have to step back a little and think
through the frame relay technology a bit....
When a router configured for frame relay boots up, it sends an LMI packet to
the frame relay switch, the frame relay switch will response to the router
and also make available to the router the various dlci numbers that can be
reached via that interface. If the router is using in inverse arp, it will
automatically obtain those dlci numbers and do all the mappings itself, but
if inverse arp is disable, the router will use the dlci configured either on
the 'frame-relay map' or on the 'frame-relay interface-dlci' statement. If
the value of the dlci configured on the router is the same with what the
switch have, your pvcs status will be 'active' and meaning your layer 2
stuff are good.
If the dlci configured locally and the frame relay switch is sending are not
the same, you will get 'deleted' or 'inactive' status if you view your pvc.
Deleted, is the frame relay switch telling you that, the dlci you configured
on your router might be wrong, Inactive is saying the dlci configured on the
remote side might be wrong.
Now, you can see the role of the frame relay switch and LMI, now when you
connect two routers back-to-back and do frame-relay encapsulation, the first
thing both of them will do is send LMI to the frame relay switch, both
router will keep waiting for a frame relay switch, so that they can
negotiate layer 2 stuff, since none of the routers is a frame relay switch,
your layer 2 will not get setup and your frame relay link will not come up,
to resolve this problem, you have to disable LMI on both routers. eg
R1#no keepalive
Now, you have disable LMI communication between both routers, but you must
find a way of telling each router what the data link CONNECTION IDENTIFIER
(dlci) is? Think of a connection identifier as a logical path between both
routers, if each router have a different path, the frame relay will be there
to switch traffic from one path to the other, but in the absence of a frame
relay switch, each router must be communicating on the same path, for them
to hear each other talk, that one and only path can only be defined by
giving both router the same DLCI number.
So, with this setup, once the routers comes on, LMI disable, no looking for
frame relay switch, R1 will automatically start talking via the path (DLCI
#) configured on it, believing that someone will hear him, lucky enough we
have equally tricked R2 to believe that that path (DLCI #) belong to him, so
he will listen and response.
Have you bridged (hardware not software) telephone extensions wiring closet
or at home before....:) ...Thats exactly what I am talking about, all the
bridged handset will have the same telephone ext. number eg ext 111. If
someone in room 1, pickes up a bridged handset 1, he can easily talk to the
second bridged handset in room 2, on the same ext 111, without dialing a
different ext. number.
I hope this helped a little bit.
Others are free to comment, add, delete, refine, etc
my 0.2
---- Godswill Oletu----- Original Message ----- From: "jellyboy" <jellyboy@gmail.com> To: <ccielab@groupstudy.com> Sent: Friday, July 15, 2005 6:04 AM Subject: Back-to-Back FR
> Hi, I have a number of questions regarding Back-to-Back FR. Two > routers R1 and R3 connected together with no FR switch in between. > > R3 config > > frame-relay switching > ! > > interface Serial0/1 > no ip address > encapsulation frame-relay > clockrate 56000 > frame-relay intf-type dce > ! > interface Serial0/1.31 point-to-point > des to r1 circuit > ip address 172.16.31.2 255.255.255.252 > frame-relay interface-dlci 31<<must be same on both sides > > R1 config > > interface Serial0/3.31 point-to-point > des to r3 circuit > ip address 172.16.31.1 255.255.255.252 > frame-relay interface-dlci 31<<must be same on both sides > > Question- why do the dlci values have to be the same value on both sides? > Question- does anyone know of any other configs that would achieve the > same result? > > Just curious, as usual! > > Cheers, > > > jellyboy > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
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