Dial Ip Backup Connection for Primary Frame Relay ConnectionSummaryIn the following example the customer desires to have a Lucent PortMaster (Tm) router at the host site connect to another PortMaster router using a Frame Relay via synchronous ports. However, if that connection is interrupted the remote router automatically dials the host router using a modem or an ISDN connection. Local Management Interface (LMI) or Annex-D polling is used to determine when the Frame Relay link is down. To set this up tell the remote router that its default gateway is the Ethernet IP address of the host router but with a high metric, like 4. The remote router must to listen for default routes on its Frame Relay interface. When one of the following three conditions occurs, the remote router will no longer have a default route via the Frame Relay interface. It falls back to the default route with the higher metric, causing it to dial out to the host router using one of its serial ports. When the Frame Relay connection returns, the default route will be learned again using Routing Information Protocol (RIP); the backup connection (analog, ISDN) will eventually time out due to lack of traffic and hang up. ConfigurationNOTE: Similar configurations can be used for connections other than Frame Relay. On the Remote Router:
IMPORTANT: The critical point to understand in making this possible is that the PortMaster does not update its routing table with learned dynamic routes which it has a static route for, EXCEPT for the default route. If the PortMaster learns a default route from RIP that has a better metric than its static default route, it will update its routing table with the "preferred" default route and "push down" the static default route. The route is hidden but still available for future use should the dynamically learned default route disappear. The three conditions that can trigger dial out are:
On the Host Router:
Example ConfigurationIP Addresses: Host Site ether0 192.168.1.1 frm1 192.168.3.1 Remote Site ether0 192.168.2.1 frm1 192.168.3.2 Host Site +------------+ | Gateway Router |------->Internet +-------e0-------+ 192.168.1.254/| | ====ETHERNET=192.168.1.0/24========== | |/192.168.1.1 +------e0------+ | Host | | Router S0--[MODEM/TA]---+ +-----frm1-----+ | |\192.168.3.1 | | | FRAME RELAY | 192.168.3.0/24 | | | |/192.168.3.2 | +-----frm1-----+ | | Remote | | | Router S0--[MODEM/TA]---+ +------e0------+ |\192.168.2.1 | ====ETHERNET=192.168.2.0/24========== Remote Site Note: The synchronous ports on PortMaster routers ALWAYS require an external clock source. The Telephone Company, the CSU/DSU or a Terminal Adapter (TA) must provide clocking to the PortMaster synchronous port. On the remote router you have a similar configuration: Command> set ether0 address 192.168.2.1 # Set the global settings Command> set gateway 192.168.1.1 4 # Set gateway 4 or higher Command> set default listen Note: Get the Frame Relay interface working before setting up the backup link. Otherwise, the backup will activate. # Configure Frame Relay connection (Primary connection) Command> set s1 protocol frame Command> set s1 address 192.168.3.2 Command> set s1 lmi 10 Command> set s1 routing broadcast # If your CSU/DSU can assert carrier, "modem on" would be useful in this setup. Command> set s1 modem off # Configure Dial out port (analog) S2 is used in the example. Command> set s2 network dial out Command> set s2 protocol ppp Command> set s2 modem on Command> set s2 xon/xoff off Command> set s2 rts/cts on Command> set s2 group 2 # Group number must match group number in location. # Create on demand location to dial up back up connection to host router Command> add location host_rtr Command> set location host_rtr on_demand Command> set location host_rtr address 192.168.1.1 Command> set location host_rtr netmask 255.255.255.0 # Netmask of host network Command> set location host_rtr routing broadcast Command> set location host_rtr protocol ppp Command> set location host_rtr mtu 1500 Command> set location host_rtr idletime 5 # Drop connection after 5 minutes idle time Command> set location host_rtr maxports 1 Command> set location host_rtr group 2 # Replaced 5551212 with telephone number for remote router. Command> set location remote script 1 "atdt5551212" "=DCD=" Command> save all Command> reset s1 Command> reset s2 On the host router you have a similar configuration. The host router MUST have a default gateway set for this setup to work. # Configure Ethernet Interface Command> set ether0 address 192.168.1.1 # Configure Global Settings Command> set gateway 192.168.1.254 # IP address of next hop to 1 or upstream # Configure Frame Relay Connection Command> set s1 protocol frame Command> set s1 address 192.168.3.1 Command> set s1 lmi 10 Command> set s1 routing listen Command> set s1 modem off # Configure Serial port for dialin (analog) Command> set s2 network dialin Command> set s2 protocol ppp Command> set s2 modem on Command> set s2 xon/xoff off Command> set s2 rts/cts on Command> set s2 idle 5 # Drop connection after 5 minutes idle time # Configure user profile for dial in Command> add netuser remote Command> set user remote protocol ppp Command> set user remote password xyzzy Command> set user remote address 192.168.2.1 # OR 255.255.255.255 to negotiate Command> set user remote routing listen # Save Configuration and reset ports. Command> save all Command> reset s1 Command> reset s2 |