Trying to cross connect two HDLC cards on two 5305 routers. Is this possible

[dchmura]

In a disaster, if I lost a 5660 router and had to fall back to a 5305 while waiting for repair or replacement. I need 3 ethernet ports, but only have 2 and an HDLC.  I have a 5305 and 5660 sitting next to each other and directly connect with Cat5.  If I could do the same with coax, I could keep my emergency rooms up until repair.

[jayh · Accepted solution]

HDLC is an encapsulation, not an interface type. Because you mention coax, you're probably dealing with T3 interfaces.

Connect the TX of one side to the RX of the other side and vice-versa. Configure one of the devices as clock source internal and the other as clock source line received from the interface. It doesn't matter which is which. Assign IPs within the same subnet to the interfaces and appropriate static routes or configure dynamic routing protocols to use the link as appropriate.

If there's an option for line build-out (LBO) or cable length, set it to 0 or short length cable.

The cable is a 75-ohm co-ax with BNC type connectors. Search for "Dual 735 cable" if you don't have it on hand.