Dual ISP connections and BGP

[TRACY HARTMANN]

I have 1 router with 3 ethernets.

2 of interfaces are ISP connections and I would prefer to 1 over the other.  I added the weight command to neighbor statement.  It took a while but it did start to prefer that.  I want to make sure this is all I need to do to prefer this ISP over the other.   I don't want it to flip unless we have an isssue with the preferred ISP circuit.

The 3rd interface is local subnets that are populated into BGP.

[Georg Pauwen]

Hello,

weight is actually your best choice, since it is the first attribute for best path selection on a Cisco router. There is no way it can 'flip', so you should be fine.

[paul driver]

Hello

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@Georg Pauwen wrote:

Hello,

There is no way it can 'flip', so you should be fine.

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Disagree, you can manaully shutdown a neigbour bgp peering to accomplish such a task
router bgp xx
neighbour x.x.x.x shutdown

[Georg Pauwen]

I agree, there are even more ways to 'flip' this:

1. Pour a bucket of water over the router

2. Set the router on fire

3. Smash the router with a sledgehammer

Just kidding. I meant under normal operation of course, without manual intervention. I thought that was obvious...:)

[paul driver]

Hello
If you have a single wan rtr with dual isp ebgp peering then bgp weight attribute is applicable for egress traffic from your lan, and the reason why you say it took a while for that the weight to be appllied to your received routes is because after you applied the weight attribute you should have performed a soft reset on the bgp peers which would have applied the changes straight away to the bgp rib

(clear ip bgp soft * in/out)
The other thing you need to consider is ingress traffic from your ISP, I assume you would like the return traffic come via the same ISP your egress and to do that you could use as-path prepending on the least preferred ISP

route-map prepend
set as-path prepend <local ASN  local ASN local ASN>
router bgp xx
neigbourt <isp2> route-map prepend out

[MHM Cisco World]

100% right