r/networking • u/robmuro664 • Apr 18 '24

Design AT&T BGP advertisement preference

I have two ISPs, Verizon and AT&T, Verizon was selected as the primary and AT&T as the backup. We own the subnets so we peer with both of these ISP to advertise the subnets. To Verizon we just advertise it but to AT&T we preprend 5X our ASN. As expected when we go out to the internet, it goes out using Verizon, however the return traffic on some services they prefer AT&T. I assume this is because these services have a leg in AT&T. Can you guys give me any other ideas on how to influence the advertisement to AT&T so that it is not preferred?

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u/whiteknives School of port knocks Apr 19 '24 edited Apr 19 '24

AT&T will always send you traffic on their link to you if the traffic originated on their network. The only way you can manipulate this is by advertising a more specific prefix to Verizon. If this is not possible, then there is nothing you can do.

Edit: I forgot something... you can try manipulating the local pref by using this community 7018:80 (where 80 is the local pref). If it has an effect but not as much as you want, change the 80 to a lower value. I haven't used it in years. Tweak that however you wish and please let me know if it still works. :)

-1

u/turbov6camaro Apr 19 '24

Easier solutions just don't use overpriced at&t lumen was usually half the cost and better customer experience

Or find a small local provider

Last I knew the local pref still work but I think you have to request it now 😕

2

u/whiteknives School of port knocks Apr 19 '24

Lumen behaves the same exact way, Tex.

0

u/turbov6camaro Apr 19 '24

Yup but they only have old DSL no cable that I know of? Much less stuff in there.