From: Joseph Brunner (joe@affirmedsystems.com)
Date: Sat Jul 05 2008 - 19:20:08 ART
Good afternoon,
Perhaps someone can shed some light on this strange, vexing issue.
Normally we are lead to believe that the "redistribute" command
redistributes routes that are in the routing table using the protocol
referenced by the redistribute command. However I have a situation where I'm
running EBGP between two edge routers and the isp routers. These router DO
NOT run IBGP between them. They DO run EIGRP between them. Eigrp is
configured to redistribute bgp learned routes, so that the default route
learned from the isp and redistributed to EIGRP learned internally.
However the following is happening;
1. Eigrp is automatically redistributing the bgp holddown routes static
to null0 (used to keep the routes in the bgp table permanently). Each Edge
router is configured with identical static routes to null for the netblocks
advertised into bgp.
2. The edge router with the the superior metric configured for the
bgp-> eigrp redistribute command is becoming the router advertising these
static routes into eigrp as external routes. So while eigrp is only
configured with "redistribute bgp" they are indeed redistributing static
routes (the hold down routes to null0), as IF THE "REDISTRIBUTE STATIC"
command had been configured under router eigrp.
3. This is causing the "show ip bgp" output on the egde router picking
up the eigrp static routes to list the other router's eigrp neighbor address
as the "next hop" while is should be 0.0.0.0 (originated on this router).
The EDGE router with the inferior metric in the "redistribute bgp" command
under router eigrp see's this.
4. How is this possible?????!?!?! Why is "redistribute bgp 65000" under
router eigrp matching the bgp table, not the routes know via bgp!
Please check the below.
NYCORPHQ1#show ip bgp
BGP table version is 4, local router ID is 10.74.74.11
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 66.66.1.1 0 0 11401 i
*> 66.55.5.0/25 0.0.0.0 0 32768 i
*> 66.55.5.128/25 0.0.0.0 0 32768 i
NYCORPHQ1#show ip route
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, su - IS-IS summary, 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 66.66.1.1 to network 0.0.0.0
66.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 66.66.1.0/30 is directly connected, Serial0/0
S 66.55.5.0/25 is directly connected, Null0
S 66.55.5.128/25 is directly connected, Null0
C 192.168.5.0/24 is directly connected, FastEthernet0/1
10.0.0.0/8 is variably subnetted, 7 subnets, 3 masks
C 10.74.74.11/32 is directly connected, Loopback1
D 10.74.74.12/32 [90/156160] via 10.10.10.2, 00:07:03, FastEthernet1/0
C 10.10.10.0/24 is directly connected, FastEthernet1/0
C 10.1.1.0/30 is directly connected, FastEthernet0/0
D 10.74.74.1/32 [90/409600] via 10.1.1.2, 00:07:03, FastEthernet0/0
D 10.1.1.4/30 [90/284160] via 10.10.10.2, 00:07:04, FastEthernet1/0
D 10.254.0.0/24 [90/284160] via 10.1.1.2, 00:07:04, FastEthernet0/0
B* 0.0.0.0/0 [20/0] via 66.66.1.1, 00:08:51
NYCORPHQ2#show ip bgp
BGP table version is 4, local router ID is 10.74.74.12
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 66.66.2.1 0 0 11401 i
*> 66.55.5.0/25 10.10.10.1 307200 32768 i
*> 66.55.5.128/25 10.10.10.1 307200 32768 i
NYCORPHQ2#show ip route
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, su - IS-IS summary, 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 66.66.2.1 to network 0.0.0.0
66.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 66.66.2.0/30 is directly connected, Serial1/0
D EX 66.55.5.0/25 [170/307200] via 10.10.10.1, 00:06:35, Ethernet0/1
D EX 66.55.5.128/25 [170/307200] via 10.10.10.1, 00:06:35, Ethernet0/1
10.0.0.0/8 is variably subnetted, 7 subnets, 3 masks
D 10.74.74.11/32 [90/409600] via 10.10.10.1, 00:06:35, Ethernet0/1
C 10.74.74.12/32 is directly connected, Loopback1
C 10.10.10.0/24 is directly connected, Ethernet0/1
D 10.1.1.0/30 [90/307200] via 10.10.10.1, 00:06:35, Ethernet0/1
[90/307200] via 10.1.1.6, 00:06:35, Ethernet0/0
D 10.74.74.1/32 [90/409600] via 10.1.1.6, 00:06:35, Ethernet0/0
C 10.1.1.4/30 is directly connected, Ethernet0/0
D 10.254.0.0/24 [90/284160] via 10.1.1.6, 00:06:35, Ethernet0/0
B* 0.0.0.0/0 [20/0] via 66.66.2.1, 00:07:41
NYCORPHQ1#show run
interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.252
duplex auto
speed auto
!
interface Serial0/0
ip address 66.66.1.2 255.255.255.252
ip virtual-reassembly
clock rate 2000000
!
interface FastEthernet1/0
ip address 10.10.10.1 255.255.255.0
ip virtual-reassembly
speed 10
full-duplex
!
router eigrp 10
redistribute bgp 65000 metric 10000 100 255 1 1500
network 10.0.0.0
no auto-summary
!
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 66.55.5.0 mask 255.255.255.128
network 66.55.5.128 mask 255.255.255.128
neighbor 66.66.1.1 remote-as 11401
neighbor 66.66.1.1 route-map nycorphq1 out
no auto-summary
!
ip forward-protocol nd
ip route 66.55.5.0 255.255.255.128 Null0 254
ip route 66.55.5.128 255.255.255.128 Null0 254
!
!
no ip http server
no ip http secure-server
!
!
ip prefix-list 66.55.5.0-25 seq 5 permit 66.55.5.0/25
!
ip prefix-list 66.55.5.128-25 seq 5 permit 66.55.5.128/25
!
route-map nycorphq1 permit 10
match ip address prefix-list 66.55.5.0-25
set metric 50
!
route-map nycorphq1 permit 20
match ip address prefix-list 66.55.5.128-25
set metric 500
!
!
!
!
control-plane
!
NYCORPHQ2#show run
!
interface Ethernet0/0
ip address 10.1.1.5 255.255.255.252
half-duplex
!
interface Ethernet0/1
ip address 10.10.10.2 255.255.255.0
ip virtual-reassembly
full-duplex
!
interface Ethernet0/2
no ip address
shutdown
half-duplex
!
interface Ethernet0/3
no ip address
shutdown
half-duplex
!
interface Serial1/0
ip address 66.66.2.2 255.255.255.252
ip virtual-reassembly
serial restart-delay 0
clock rate 2016000
!
interface Serial1/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
router eigrp 10
redistribute bgp 65000 metric 1500 100 255 1 1500
network 10.0.0.0
no auto-summary
!
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 66.55.5.0 mask 255.255.255.128
network 66.55.5.128 mask 255.255.255.128
neighbor 66.66.2.1 remote-as 11401
neighbor 66.66.2.1 route-map nycorphq2 out
no auto-summary
!
no ip http server
no ip http secure-server
!
ip forward-protocol nd
ip route 66.55.5.0 255.255.255.128 Null0 254
ip route 66.55.5.128 255.255.255.128 Null0 254
!
!
!
ip prefix-list 66.55.5.0-25 seq 5 permit 66.55.5.0/25
!
ip prefix-list 66.55.5.128-25 seq 5 permit 66.55.5.128/25
!
route-map nycorphq2 permit 10
match ip address prefix-list 66.55.5.128-25
set metric 50
!
route-map nycorphq2 permit 20
match ip address prefix-list 66.55.5.0-25
set metric 500
!
!
!
control-plane
!
!
!
!
This archive was generated by hypermail 2.1.4 : Mon Aug 04 2008 - 06:11:53 ART