11-02-2009 11:24 AM - edited 03-04-2019 06:35 AM
Dear All,
This is my recent problem i faced in my network by having loops created in network and network going shut or performence fail for some sites.
In details , my network is having two 7600 routers connected to service provider by BGP with 4 and 2 MB link respectively.I use EIGRP at my core switch ,for my internal network. My getting routes from all my remotes sites on both links if used shutting down one router.If both routers are switched on,my both routers are learing same routes and creating loops in network and network fails.
Some how i found that i can make load balancing by using IBGP between two routers.
Couldn anyone please let me knew further detail process for same.
Sami
11-02-2009 11:41 AM
Hello Sami,
your core switches are running both BGP and EIGRP.
you are probably redistributing BGP into EIGRP but also EIGRP into BGP.
mutual redistribution requires additional safety measures.
an iBGP session can help but:
BGP can advertise EIGRP routes by using appropriate network commands that match EIGRP prefixes (including EIGRP summary routes if needed).
this can help by eliminating redistribution of EIGRP into BGP.
once you remove mutual redistribution you should be fine.
alternatively, if mutual redistribution is needed for any reason you need to implement route tags and route-tags filtering as in this example:
route-map BGPtoEIGRP deny 10
match route-tag 500
route-map BGPtoEIGRP permit 20
set route-tag 600
route-map EIGRPtoBGP deny 10
match route-tag 600
route-map EIGRPtoBGP permit 20
set route-tag 500
the idea is that what is learned by BGP at core1 has to be filtered in redistributing to BGP at core2.
And also for EIGRP the same idea
router bgp xx
redistribute eigrp 100 route-map EIGRPtoBGP
router eigrp 100
red bgp xx route-map BGPtoEIGRP
if we put iBGP session in the picture we can get some benefits but I'm not sure that loops are solved without the safety measures described above.
Hope to help
Giuseppe
11-05-2009 12:49 AM
Please find below Configuration for 2 routers and core switch
Router 1
interface GigabitEthernet0/0.127
description " WiMax 2Mbps DMAM09-DMAM09 IP31 "
bandwidth 2048
encapsulation dot1Q 127
ip address 172.31.83.182 255.255.255.252
ip flow ingress
!
interface GigabitEthernet0/1
description DMAM09_00_303-DMAM09_00_303 IP4 Fiber 4Mbps
bandwidth 4096
no ip address
ip flow ingress
ip flow egress
load-interval 30
duplex auto
speed auto
media-type rj45
!
interface GigabitEthernet0/1.123
description DMAM09_00_303-DMAM09_00_303 IP4 Fiber 4Mbps
bandwidth 4096
encapsulation dot1Q 123
ip address 172.31.178.110 255.255.255.252
ip flow ingress
ip flow egress
traffic-shape group 130 512000 12800 12800 1000
!
router eigrp 100
redistribute static
redistribute bgp 64589 metric 1000 10 255 1 1500
network 10.0.0.0
no auto-summary
no eigrp log-neighbor-changes
!
router bgp 64589
bgp log-neighbor-changes
neighbor 172.31.28.237 remote-as 65000
neighbor 172.31.178.109 remote-as 65000
!
address-family ipv4
redistribute static
redistribute eigrp 100
neighbor 172.31.28.237 activate
neighbor 172.31.178.109 activate
no auto-summary
no synchronization
Router 2:
interface GigabitEthernet0/0.127
description " WiMax 2Mbps DMAM09-DMAM09 IP31 "
bandwidth 2048
encapsulation dot1Q 127
ip address 172.31.83.182 255.255.255.252
ip flow ingress
shutdown
!
interface GigabitEthernet0/1
ip address 10.42.0.18 255.255.255.252
ip hello-interval eigrp 100 1
ip hold-time eigrp 100 3
ip authentication mode eigrp 100 md5
ip authentication key-chain eigrp 100 SPO@AuthIP100
no ip mroute-cache
duplex auto
speed 100
media-type rj45
!
interface FastEthernet0/0/0
description Link to DMHF5C1CrS2C65
ip address 10.42.0.6 255.255.255.252
ip access-group 30 out
no ip proxy-arp
ip hello-interval eigrp 100 1
ip hold-time eigrp 100 3
ip authentication mode eigrp 100 md5
ip authentication key-chain eigrp 100 SPO@AuthIP100
no ip mroute-cache
duplex auto
speed auto
!
interface FastEthernet0/0/1
description Link to DMHF5C1CrS2C65
ip address 10.43.0.6 255.255.255.252
ip access-group 30 out
no ip proxy-arp
ip hello-interval eigrp 100 1
ip hold-time eigrp 100 3
ip authentication mode eigrp 100 md5
ip authentication key-chain eigrp 100 SPO@AuthIP100
no ip mroute-cache
duplex full
speed 100
!
router eigrp 100
redistribute bgp 64589 metric 1000 10 255 1 1500
network 10.0.0.0
no auto-summary
no eigrp log-neighbor-changes
!
router bgp 64589
bgp log-neighbor-changes
neighbor 172.31.28.237 remote-as 65000
neighbor 172.31.83.181 remote-as 65000
!
address-family ipv4
redistribute eigrp 100
neighbor 172.31.28.237 activate
neighbor 172.31.83.181 activate
no auto-summary
no synchronization
Core switch Routing :
router eigrp 100
redistribute connected
redistribute static
network 10.0.0.0
distribute-list default-Route out !
ip classless
ip route 0.0.0.0 0.0.0.0 10.42.0.2
!
no ip http server
!
ip access-list standard default-Route
permit 0.0.0.0
!
access-list 186 deny tcp 10.44.0.0 0.0.255.255 10.0.152.0 0.0.0.255
access-list 186 permit ip any any
with above configuration am able to put up my network transmitting well,but when i switch on my second router the loops are found and network gets down.please let me knew the simple method with minimum down time to remove my loopps and utilize both links of 4 and 2 mbps in my network to same ISP.
11-05-2009 05:15 AM
Hello Sami,
as I have guessed in my first post the problem is that you have two devices performing mutual redistribution between BGP and EIGRP.
I've already explained the two options available:
a) removing red of EIGRP into BGP and adding appropriate network commands under router BGP to represent local routes
b) using route tags to implement mutual redistribution in a controlled way
also on core switches what is the use of ip route 0.0.0.0 0.0.0.0 10.42.0.2 if they receive the default route in EIGRP this is not needed.
in this way you are overriding the dynamic routing.
I'm afraid this can be part of the problem. Also I would try to remove the distribute-list to see what happens.
Hope to help
Giuseppe
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