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Configuring serial connection between Juniper Firewall and a Cisco router using PPP encapsulation

  [KB10530] Show Article Properties


Summary:
Serial interface on the Juniper Firewall is not coming UP when connecting to Cisco router.
Symptoms:
Serial interface on the Juniper Firewall is not coming UP when connecting to Cisco router.
Solution:
Setup is as below:
SSG20------CSU/DSU========T1==========Cisco Router

The SSG20 is connected to an external CSU/DSU using a DB60 to V.35 serial cable.  Cable between the external CSU/DSU to the Cisco router (with built-in CSU/DSU) is a X-over T1.

Physical link issues:
  • If  the output of the command, get int <int_name>, reports phy-link down, then check the cabling.

Protocol link issues:
  • If  the output of the command, get int <int_name>, reports link down and phy-link up, then the Physical link is up but the protocol link is down, so check the following:

1) Basic PPP configuration on the SSG20:

set int s1/0 encap ppp
set ppp profile test
set ppp profile test static-ip
set int s1/0 ip
set int s1/0 ppp profile test
set int s1/0 serial-options dte-options ignore-all

Note:  It is very important to have the PPP profile set. Also, the "dte-options ignore-all" is only for convenience so that the firewall can accept all CSU/DSU settings.

2) Make sure the settings on the CSU/DSU, such as speed and channels, match the settings on the Cisco end.

3) Lastly, make sure the contoller and serial interface on the Cisco is in good condition. The following is a sample PPP configuration on the Cisco router:

controller T1 0/2
 framing esf
 clock source internal
 linecode b8zs
 channel-group 0 timeslots 1-24

interface Serial0/0
 ip address 1.1.1.2 255.255.255.0
 encapsulation ppp
 no fair-queue
 service-module t1 timeslots 1-24
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