WAN connection problem

Dear Sir,
i have WAN connection point to point,with 3 the lines yesterday we faced that we lost the connection with the brance when we checked with Centeral office he informed that the problem not from the lines and it may be from the routers the statues of the interfaces as below :
Serial1/0                  unassigned      YES NVRAM  up                    down

Serial1/1                  unassigned      YES NVRAM  up                    down

Serial1/2                  unassigned      YES NVRAM  up                    down

i need to know is it the problem from the routers or not of from lines.the below is the statues of debug ppp error :
1d15h: Se1/1 LCP: ID 119 didn't match 176, discarding packet
1d15h: Se1/0 LCP: ID 177 didn't match 119, discarding packet
1d15h: Se1/1 LCP: ID 120 didn't match 177, discarding packet
1d15h: Se1/0 LCP: ID 178 didn't match 120, discarding packet
1d15h: Se1/1 LCP: ID 121 didn't match 178, discarding packet
1d15h: Se1/0 LCP: ID 179 didn't match 121, discarding packet
1d15h: Se1/1 LCP: ID 122 didn't match 179, discarding packet
1d15h: Se1/0 LCP: ID 180 didn't match 123, discarding packet
1d15h: Se1/1 LCP: ID 124 didn't match 180, discarding packet
1d15h: Se1/0 LCP: ID 181 didn't match 124, discarding packet
1d15h: Se1/1 LCP: ID 125 didn't match 182, discarding packet
1d15h: Se1/0 LCP: ID 183 didn't match 125, discarding packet
1d15h: Se1/1 LCP: ID 126 didn't match 183, discarding packet

so please advise how to troubleshoot  the problem.i make interface multilink to bundle the 3 interfaces.the protocal i used on the 3 interfaces is ppp
interface Multilink1
 ip address 10.1.1.2 255.255.255.252
 ip route-cache flow
 ppp multilink
 multilink load-threshold 1 outbound
 multilink-group 1

interface Serial1/0
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Serial1/1
 no ip address
 encapsulation ppp
 shutdown
 ppp multilink
 multilink-group 1
!
interface Serial1/2
 no ip address
 encapsulation ppp
 shutdown
 ppp multilink
 multilink-group 1

the router i use in both sites is cisco 3600
shareef_yassinAsked:
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JustInCaseCommented:
Your interfaces s1/1 & s1/2 are shut
interface Serial1/1
 no ip address
 encapsulation ppp
 shutdown
and physical lines are up????
Serial1/1                  unassigned      YES NVRAM  up                    down
0
shareef_yassinAuthor Commented:
yes i was shut down to test each but kindly find the below after i run no shut

Serial1/0                  unassigned      YES NVRAM  up                    down

Serial1/1                  unassigned      YES NVRAM  up                    down


interface Multilink1
 ip address 10.1.1.2 255.255.255.252
 ip route-cache flow
 no cdp enable
 ppp multilink
 multilink load-threshold 1 outbound
 multilink-group 1



!
interface Serial1/0
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Serial1/1
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Serial1/2
 no ip address
 encapsulation ppp
 ppp multilink
 multilink-group 1
0
naderzCommented:
Looks like You are bundling three T1s together. That means both sides must match their configuration. If you are getting a Up/Down on the Interface that means your configuration (Protocol) with the far end does not match. Has there been any changes at either your side or the far end?

Again, the first Up means you are OK on Layer 1. The second Down means your not OK on Layer 2 (Protocol).

What do you get when you run "show interface serial 1/0, serial 2/0, etc"? Look at the errors and counters.  Also, check "show ppp interface serial 1/0; serial 2/0; 3/0"
0
shareef_yassinAuthor Commented:
it was ISP problem
0

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shareef_yassinAuthor Commented:
bcz it was ISP problem not related to router
0
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