RIP and Frame Relay Hub & Spoke
This is a hub and spoke
topology :
R1 is the hub, r2 and r3 are the
spokes.
RIP, Hub & Spoke and main-interfaces
Working with RIPv1 (but almost the same with RIPv2) :
R1 :
!
interface FastEthernet0/0
ip address 150.123.1.1 255.255.255.0
!
interface Serial1/0
ip address 150.123.0.1 255.255.255.0
encapsulation frame-relay
!
router rip
redistribute connected route-map
CONNECTED->RIP
network 150.123.0.0
!
route-map CONNECTED->RIP permit 10
match interface FastEthernet0/0
!
R2 :
!
interface FastEthernet0/0
ip address 150.123.2.2 255.255.255.0
!
interface Serial1/0
ip address 150.123.0.2 255.255.255.0
encapsulation frame-relay
frame-relay map ip 150.123.0.3 201
!
!
router rip
redistribute connected route-map
CONNECTED->RIP
network 150.123.0.0
!
route-map CONNECTED->RIP permit 10
match interface FastEthernet0/0
!
R3 :
!
interface FastEthernet0/0
ip address 150.123.3.3 255.255.255.0
!
interface Serial1/0
ip address 150.123.0.3 255.255.255.0
encapsulation frame-relay
frame-relay map ip 150.123.0.2 301
!
!
router rip
redistribute connected route-map
CONNECTED->RIP
network 150.123.0.0
!
route-map CONNECTED->RIP permit 10
match interface FastEthernet0/0
!
r3#sh ip route
150.123.0.0/24 is subnetted, 4 subnets
R
150.123.1.0 [120/1] via 150.123.0.1, 00:00:26, Serial1/0
C
150.123.0.0 is directly connected, Serial1/0
C
150.123.3.0 is directly connected, FastEthernet0/0
R
150.123.2.0 [120/2] via 150.123.0.1, 00:00:26, Serial1/0
r3#ping 150.123.2.2 source 150.123.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to
150.123.2.2, timeout is 2 seconds:
Packet sent with a source address of
150.123.3.3
!!!!!
Success rate is 100 percent (5/5),
round-trip min/avg/max = 44/44/44 ms
r1#sh ip route
150.123.0.0/24 is subnetted, 4 subnets
C
150.123.1.0 is directly connected, FastEthernet0/0
C
150.123.0.0 is directly connected, Serial1/0
R
150.123.3.0 [120/1] via 150.123.0.3, 00:00:25, Serial1/0
R
150.123.2.0 [120/1] via 150.123.0.2, 00:00:00, Serial1/0
r1#
r1#sh
ip protocols
***
IP Routing is NSF aware ***
Routing
Protocol is "rip"
Sending updates every 30 seconds, next due in
15 seconds
Invalid after 180 seconds, hold down 180,
flushed after 240
Outgoing update filter list for all
interfaces is not set
Incoming update filter list for all
interfaces is not set
Redistributing: connected, rip
Default version control:
send version 1, receive any version
Interface Send Recv
Triggered RIP Key-chain
FastEthernet0/0 1
1 2
Serial1/0 1 1 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
150.123.0.0
Routing Information Sources:
Gateway
Distance Last Update
150.123.0.3 120 00:00:08
150.123.0.2 120 00:00:11
Distance: (default is 120)
On the physical interface,
split-horizon is disabled. When r1 receives a RIP update on s1/0, it sends back
this RIP update on s1/0. This allows each router spokes to have good routing
information.
Check :
r1#show ip interface s1/0
Serial1/0 is up, line protocol is up
Internet address is 150.123.0.1/24
(...)
Multicast reserved groups joined: 224.0.0.9
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Local Proxy ARP is disabled
Security level is default
Split horizon is disabled
ICMP redirects are always sent
(...)
Note: even with RIPv1, the interface
receives RIPv2 updates, so the interface has joined 224.0.0.9.
RIP, Hub & Spoke and sub-interfaces
Now, the hub is connected to the
Frame-Relay switch via a sub-interface.
r1#sh run int s1/0.123
Building configuration...
Current configuration : 144 bytes
!
interface Serial1/0.123 multipoint
ip address 150.123.0.1 255.255.255.0
frame-relay interface-dlci 102
frame-relay interface-dlci 103
end
As it is a sub-interface, dlci must be
specified. Dynamic mapping is still in use :
r1#show frame-relay map
Serial1/0.123 (up): ip 150.123.0.2
dlci 102(0x66,0x1860), dynamic,
broadcast,
CISCO, status defined, active
Serial1/0.123 (up): ip 150.123.0.3
dlci 103(0x67,0x1870), dynamic,
broadcast,
CISCO, status defined, active
r1 still receives RIP updates from r2
and r3 :
r1#sh ip route rip
150.123.0.0/24 is subnetted, 4 subnets
R
150.123.3.0 [120/1] via 150.123.0.3, 00:00:10, Serial1/0.123
R
150.123.2.0 [120/1] via 150.123.0.2, 00:00:04, Serial1/0.123
r1#
But r2 doesn’t receives r3’s updates
and vice-versa :
r2#show ip route rip
150.123.0.0/24 is subnetted, 3 subnets
R
150.123.1.0 [120/1] via 150.123.0.1, 00:00:24, Serial1/0
r3#show ip route rip
150.123.0.0/24 is subnetted, 3 subnets
R
150.123.1.0 [120/1] via 150.123.0.1, 00:00:12, Serial1/0
This is because split-horizon is
enabled on s1/0.123 on r1 :
r1(config-subif)#do sh ip int
s1/0.123
Serial1/0.123 is up, line protocol is
up
Internet address is 150.123.0.1/24
Broadcast address is 255.255.255.255
(...)
Split horizon is enabled
(...)
Then :
r2#s ip route rip
150.123.0.0/24 is subnetted, 4 subnets
R
150.123.1.0 [120/1] via 150.123.0.1, 00:00:00, Serial1/0
R
150.123.3.0 [120/2] via 150.123.0.1, 00:00:00, Serial1/0
r3#sh ip route rip
150.123.0.0/24 is subnetted, 4 subnets
R
150.123.1.0 [120/1] via 150.123.0.1, 00:00:17, Serial1/0
R
150.123.2.0 [120/2] via 150.123.0.1, 00:00:17, Serial1/0
r3#
Static Mapping & RIP
Disable dynamic mapping on hub & spokes.
r1#sh run int s1/0.123
Building configuration...
Current configuration : 201 bytes
!
interface Serial1/0.123 multipoint
ip address 150.123.0.1 255.255.255.0
no ip split-horizon
frame-relay map ip 150.123.0.2 102
frame-relay map ip 150.123.0.3 103
no frame-relay inverse-arp
end
The same is done on r2 and r3 :
r2#sh run int s1/0
Building configuration...
Current configuration : 237 bytes
!
interface Serial1/0
ip address 150.123.0.2 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 150.123.0.3 201
frame-relay map ip 150.123.0.1 201
no frame-relay inverse-arp
no clns route-cache
end
r3#sh run interface s1/0
Building configuration...
Current configuration : 237 bytes
!
interface Serial1/0
ip address 150.123.0.3 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 150.123.0.2 301
frame-relay map ip 150.123.0.1 301
no frame-relay inverse-arp
no clns route-cache
end
Split-horizon is still disabled on r1.
No routes are exchanged between
routers because the keyword "broadcast" hasn’t been added to the static
mapping.
r1#sh ip route rip
r1#
Two solutions exists:
1. Use unicast RIP :
r1 :
router rip
redistribute connected route-map
CONNECTED->RIP
passive-interface default
network 150.123.0.0
neighbor 150.123.0.2
neighbor 150.123.0.3
r2 :
!
router rip
redistribute connected route-map
CONNECTED->RIP
passive-interface default
network 150.123.0.0
neighbor 150.123.0.1
!
r3 :
!
router rip
redistribute connected route-map
CONNECTED->RIP
passive-interface default
network 150.123.0.0
neighbor 150.123.0.1
!
Now, RIP is working (It is the same
prinicple with RIPv2).
r2#sh ip route rip
150.123.0.0/24 is subnetted, 4 subnets
R
150.123.1.0 [120/1] via 150.123.0.1, 00:00:17, Serial1/0
R
150.123.3.0 [120/2] via 150.123.0.1, 00:00:17, Serial1/0
Note that the passive-interface command
is added because even with the neighbor statement, broadcast updates (multicast
for v2) are sent.
2. Add the broadcast keyword.
R3 :
interface Serial1/0
ip address 150.123.0.3 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 150.123.0.2 301
frame-relay map ip 150.123.0.1 301 broadcast
no frame-relay inverse-arp
no clns route-cache
On r1 :
interface Serial1/0.123 multipoint
ip address 150.123.0.1 255.255.255.0
no ip split-horizon
frame-relay map ip 150.123.0.2 102 broadcast
frame-relay map ip 150.123.0.3 103 broadcast
no frame-relay inverse-arp
Note that on the spoke routers, the
broadcast is specified once per dlci, not per mapping.
It works :
r1#sh ip route rip
150.123.0.0/24 is subnetted, 4 subnets
R
150.123.3.0 [120/1] via 150.123.0.3, 00:00:03, Serial1/0.123
R
150.123.2.0 [120/1] via 150.123.0.2, 00:00:26, Serial1/0.123
