Example 7-4 Summarization of IP Routes from Router B
Working Example for Router B
interface Ethernet0
ip address 140.100.104.1 255.255.255.0
no ip directed-broadcast
ip router isis
isis circuit-type level-1
!
interface Serial0
no ip address
no ip directed-broadcast
encapsulation frame-relay
no ip mroute-cache
no fair-queue
clockrate 56000
!
interface Serial0.2 point-to-point
ip address 140.100.32.2 255.255.255.0
no ip directed-broadcast
ip router isis
isis circuit-type level-2-only
frame-relay interface-dlci 931
!
interface Serial0.3 point-to-point
ip address 140.100.16.2 255.255.255.0
no ip directed-broadcast
ip router isis
isis circuit-type level-2-only
frame-relay interface-dlci 631
!
!
router isis
summary-address 140.100.104.0 255.255.252.0
! Routes 140.100.104.0-140.100.107.0 summarized with the /22 bit mask.
net 49.0002.0000.0000.000b.00
!
ip classless
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Configuring NBMA Frame Relay is a WAN technology that has evolved beyond the point-to-point capabilities. When configured in a full mesh, the cloud is multiaccess, although each circuit is discrete and therefore not a true broadcast medium. The configuration for IS-IS over the fully meshed Frame Relay cloud is illustrated in Figure 7-12, and there is a working example of the configuration in Example 7-5.
In Figure 7-12, the Frame Relay cloud has three fully meshed routers, which can operate as a LAN as far as IS-IS PDUs are concerned.
Figure 4 NBMA Frame Relay Cloud Running Broadcast Integrated IS-IS
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In Example 5, the frame-relay map ip command maps the IP destination address to the
outgoing DLCI and defines the interface as a broadcast interface. Integrated IS-IS uses the links as if they were truly a broadcast link and elects a DIS.
The frame-relay map clns command maps to the CLNS process on the destination router.
Without the second command, no routes appear in the IP routing table because CLNS does not receive the frames to populate the IP routing table. Remember that these are IP routes carried in the IS-IS routing protocol. It is IS-IS that updates the IP routing table.
Example 7-5 NBMA Frame Relay Cloud, Running Broadcast Integrated IS-IS
Working Example for Router A
!
interface Ethernet0
ip address 140.100.96.1 255.255.255.0
ip router isis
isis circuit-type level-1
!
interface Serial0
ip address 140.100.64.1 255.255.255.0
ip router isis
encapsulation frame-relay
clockrate 56000
frame-relay map clns 629 broadcast
!Map the layer 2 DLCI address in Frame Relay to the clns process of Router C
frame-relay map clns 931 broadcast
!Map the layer 2 DLCI address in Frame Relay to the clns process of Router B
frame-relay map ip 140.100.64.2 931 broadcast
!Map the layer 2 DLCI address in Frame Relay to the Destination IP address of Router
B
frame-relay map ip 140.100.64.3 629 broadcast
!Map the layer 2 DLCI address in Frame Relay to the Destination IP address of Router
C
isis circuit-type level-2-only
!
interface Serial1
no ip address
shutdown
!
!
router isis
net 49.0001.0000.0000.000a.00
!
ip classless
[page]
The alternative solution is to define subinterfaces and to configure each subinterface as pointto- point. This requires an IP subnet per link. Because the link is point-to-point, there is no need to configure frame-relay map commands because there is no choice of destination to define.
The point-to-point link is just a pipe that goes to one destination. As shown in the configuration, it is only necessary to configure the interface as point-to-point, start Frame Relay, and define the DLCI. As well as configuring Frame Relay, you must also start the IS-IS process for the interface.
Figure 5 supports the working example for this configuration. It shows the DLCI addresses and the IP addresses for the point-to-point links as well as the ISO addresses for the Routers A, B, and C.
Figure 5 NBMA Frame Relay Cloud Running Point-to-Point Integrated IS-IS
Example 7-6 shows the configuration for Router A to run Integrated IS-IS across the Frame Relay cloud as if it were a broadcast network.
Example 7-6 NBMA Frame Relay Cloud, Running Broadcast Integrated IS-IS
Working Example for Router A
!
interface Ethernet0
ip address 140.100.96.1 255.255.255.0
ip router isis
!
interface Serial0
no ip address
encapsulation frame-relay
!Configure Frame Relay for the interface
no fair-queue
clockrate 56000
!
interface Serial0.1 point-to-point
!Configure the subinterface to be point-to-point
ip address 140.100.64.1 255.255.255.0
ip router isis
frame-relay interface-dlci 629
!Configure Frame Relay and define the DLCI to the destination
interface Serial0.2 point-to-point
! Configure the subinterface to be point-to-point
ip address 140.100.32.1 255.255.255.0
ip router isis
frame-relay interface-dlci 931
! Configure Frame Relay and define the DLCI to the destination
!
router isis
net 49.0001.0000.0000.000a.00
!
ip classless
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