From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Thu Jun 30 2005 - 18:07:36 GMT-3
Hello
I'm having doubts regarding one thing that doc CD states very strongly:
If split horizon is enabled, neither autosummary nor interface summary
addresses (those configured with the ip summary-address rip command) are
advertised
I got curious and tried to see for my self.
The config I used is:
interface Loopback1
ip address 172.1.0.1 255.255.255.0
!
interface Loopback2
ip address 172.1.1.1 255.255.255.0
!
interface Loopback3
ip address 172.1.2.1 255.255.255.0
!
interface Loopback4
ip address 172.1.3.1 255.255.255.0
!
interface FastEthernet0/0
ip address 150.50.17.1 255.255.255.0
ip rip v2-broadcast
ip rip send version 2
ip rip receive version 2
ip summary-address rip 172.1.0.0 255.255.252.0
!
router rip
version 2
passive-interface default
no passive-interface FastEthernet0/0
network 150.50.0.0
network 172.1.0.0
network 200.0.0.0
no auto-summary
By default Ethernet interfaces do have split horizon enabled:
R1#sh ip int fa0/0
FastEthernet0/0 is up, line protocol is up
Internet address is 150.50.17.1/24
Broadcast address is 255.255.255.255
Address determined by non-volatile memory
MTU is 1500 bytes
...
Security level is default
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
...
BGP Policy Mapping is disabled
R1#
But when I do
R1#sh ip protocols
Address Summarization:
172.1.0.0/22 for FastEthernet0/0
Maximum path: 4
And if I check a router connected to R1, on its routing table I see
R2#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
200.0.0.0/32 is subnetted, 8 subnets
R 200.0.0.8 [120/7] via 150.50.100.5, 00:00:02, Tunnel25
R 200.0.0.9 [120/2] via 150.50.100.6, 00:00:02, Tunnel26
R 200.0.0.1 [120/1] via 150.50.17.1, 00:00:05, FastEthernet0/0
C 200.0.0.2 is directly connected, Loopback0
R 200.0.0.4 [120/1] via 150.50.24.4, 00:10:47, Serial0/0.24
R 200.0.0.5 [120/1] via 150.50.100.5, 00:00:02, Tunnel25
R 200.0.0.6 [120/1] via 150.50.100.6, 00:00:02, Tunnel26
R 200.0.0.7 [120/2] via 150.50.100.5, 00:00:03, Tunnel25
172.1.0.0/22 is subnetted, 1 subnets
R 172.1.0.0 [120/1] via 150.50.17.1, 00:00:06, FastEthernet0/0
<<<<<<<<<<
150.50.0.0/16 is variably subnetted, 10 subnets, 4 masks
R 150.50.6.128/25 [120/2] via 150.50.100.6, 00:00:03, Tunnel26
R 150.50.200.0/24 [120/1] via 150.50.17.1, 00:00:06,
FastEthernet0/0
R 150.50.4.0/24 [120/3] via 150.50.100.5, 00:00:03, Tunnel25
R 150.50.6.0/25 [120/1] via 150.50.100.6, 00:00:03, Tunnel26
R 150.50.7.0/25 [120/1] via 150.50.100.6, 00:00:03, Tunnel26
[120/1] via 150.50.100.5, 00:00:03, Tunnel25
C 150.50.9.0/26 is directly connected, BRI0/0
C 150.50.17.0/24 is directly connected, FastEthernet0/0
C 150.50.24.0/24 is directly connected, Serial0/0.24
C 150.50.100.0/24 is directly connected, Serial0/0.256
R 150.50.5.64/27 [120/2] via 150.50.100.5, 00:00:03, Tunnel25
R2#
Am I doing something that is not right? What am I missing here? I don't
have autosummary on, so that the 172.1.0.0/22 doesn't become
172.1.0.0/16. But according to docs I shouldn't be seeing the summarized
route, right? If I disable split horizon, the things are pretty much the
same...
Would any one please explain this to me?
Thank you
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