11-25-2008 07:28 AM - edited 03-04-2019 12:29 AM
Hello,
I am tasked with implementing BGP for incoming internet from two ISPs. I am using a 3854. The ISPs deliver internet via ethernet. The preferred provider is a 50mb link and the secondary is a 10mb link. I would like to use the preferred provider for all incoming and outgoing traffic and the secondary provider only for failover. Below is a quick dummy config I created. Any advice or suggestions would be appreciated as I think I need more in the config:
router bgp 333
network xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
neighbor 1.1.1.1 remote-as 111 --- Vendor A
neighbor 1.1.1.1 weight 200 --- Vendor A
neighbor 2.1.1.1 remote-as 222 --- Vendor B
neighbor 2.1.1.1 weight 100 --- Vendor B
interface GigabitEthernet0/0
description "Internal to Firewall"
ip address 192.168.0.2 255.255.255.0
duplex auto
speed auto
media-type rj45
interface FastEthernet1/0
description "Vendor A Primary link AS 111"
ip address 1.1.1.2 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet1/1
description "Vendor B Secondary link AS 222"
ip address 2.1.1.2 255.255.255.0
duplex auto
speed auto
bgp fast-external-fallover
11-25-2008 07:52 AM
Hello Dave,
you need additional features to influence inbound traffic:
at a minimum use AS path prepending to the backup provider
define a route-map that will be applied outbound with
set as-path prepend yourAS yourAS yourAS
if this is not enough for you needs you could consider to use BGP conditional advertisement towards the backup ISP so that you will advertise your prefixes to it only when some BGP routes are missing (a sign that the primary BGP session has failed)
see
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094309.shtml#ex3
Hope to help
Giuseppe
11-25-2008 07:54 AM
The WEIGHT attribute will force Vendor A to be the preferred exit point in your network, however, you also need to influence the return traffic to come back via Vendor A and the WEIGHT attribute alone won't do it.
If your ISPs allow it, you can use AS_PATH_PREPEND out Vendor B in order to make Vendor A the preferred ISP for the return traffic.
HTH,
__
Edison.
11-25-2008 08:03 AM
HI Dave, [Pls RATE if HELPS]
The configuration is simple. If you wish to apply the control LIST use the Route-Map with Match (Match an ACL or Prefix List) / Set (the Weight) Statements.
Refer the useful document below for the dual-homing with BGP using different ISP's
http://cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml
Hope I am informative. Pls RATE if HELPS
Best Regards,
Guru Prasad R
11-25-2008 08:17 AM
Hey dave
One small tip from me. In your scenario i asume you will be using the public ip address from primary ISP in the outside interface of you firewall(or a outside nat pool) for natting your inside networks. In that case make sure that your secondary ISP dont have any restrictions in routing the ip address range from the primary ISP with a longer as-path attribute.
Ullas
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