T1 configuration

I am replacing my current CSU/DSU and router with a CSU/DSU router combination to elimenate some equipment and save space. I have the replacement DSU/router combo ready to configure and I have called my ISP for the config info, however I am unable to decifer some of the info. I have all IP info but I believe I am missing some Serial settings. I was given the info below.  Please me decifer the info and if I am missing something what else do I need? I am fairly new at configuring T1s but very comfortable with routing.

Serial IP Information:
WAN default Gateway (PAETEC): 199.xx.xx.113
Customer Serial IP: 199.xx.xx.114
Subnet Mask:

Public LAN Network:
xx.xx.xx.104/29 [1/0] via 199.xx.xx.114, Serial1/2/3/16:23.157
Subnet Mask:
Usable Public IPs:
xxx.xx.xx.105 to xxx.xx.xx.110

The IPs I understand but I do not understand the  Serial1/2/3/16:23.157
meaning. Please help.
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alg205Author Commented:
"...but I do not understand the  Serial1/2/3/16:23.157"

Sounds like that might be referring to a physical port somewhere (maybe only of relevance to the telco).  It doesn't sound like it contains any parameters related to a T1 config.

If you know the framing/coding, timing, etc settings of your old T1 CSU/DSU, then just use that and you should be fine.


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Khandakar Ashfaqur RahmanExpert/ConsultantCommented:
xx.xx.xx.104/29 [1/0] via 199.xx.xx.114, Serial1/2/3/16:23.157

Looks like xx.xx.xx.104/29 has updated from Serial1/2/3/16:23.157 interface.Might be your WAN link is configured with point to point protocol.And, this route was configured into your ISP router.So, your router has learned this route from your ISP router.And Serial1/2/3/16:23.157 indicates subinterface of router.
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TimotiStDatacenter TechnicianCommented:
What kind of monster router uses a 4-level hierarchy in its serial interface naming? I'm amazed...
Is this supposed to be a full T1 or a fractional? It looks like fractional to me.


Is broken down as:

Serial1/2/3  - port

16:23 T1 channels to use for this port

.157 sub interface
alg205Author Commented:
I didnt have access to the old equipment (no one had the password and it was easier to just contact the ISP again for the serial timing and encapsulation) so i was unable to get that from the old router.  The ISP responded with this (all channels 1.5 MB Encapsulation: Frame Relay IETF) and that made sense to me. I configured it with timeslot 1-24 encapsulation frame-relay IETF and its up and running. By the way the Router is a Cisco 1721 with a T1 Wic. Thanks for your help. I still do not know what the original info was about but I am not going to worry about it now. Thanks for you help.
alg205Author Commented:
One more thing, I thought the samething as TimotiSt "what the heck 4 levels......not a Cisco 1721" !!!!!!!
Did a double check:


Serial 1/2/3 is port

16 is the channel group (used only for channelized T1)

23.157  sub-interface for point-2-point links

ref: http://www.cisco.com/en/US/docs/routers/access/1700/1721/software/feature/guide/t1e11721.html
Khandakar Ashfaqur RahmanExpert/ConsultantCommented:
Giltjir is right.As I mentioned before it is P2P and indicates subinterface.Giltjir described it as well.
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