Hello folks that are also "Geeking Out" over the 4th of July---
We are revamping the Internet architecture, and we are going to have a brand
new external 7507 with 1 new DS3 and 4 T1s. There will be EBGP and static
routing. Right now the T1s are on the existing external router with static
routes and OSPF. The internal router (and it's replacement 7507) has/will
have static routes and EIGRP. EIGRP is the main protocol in the netork.
Anyway, the 4 T1s will backup the DS3, but when the backup occurs, I'd like
them to load share. I read that ebgp-multihop is the technique to use when
load sharing parallel links, using the loopbacks vs. the regular neighbor
addresses.
a. Can you tell me if my proposed BGP config is correct or point out things
that are wrong or missing? Config. is below.
b. Is this backup strategy good?
c. The T1s won't be used unless the DS3 dies, right?
d. Do I need to worry about filters or attributes (like weights, local
preference, MED, etc.) in this case?
e. Oh, should I do ip route-cache or no ip route-cache on the T1s and DS3?
I figure leave the defaults ip route-cache to save on CPU cycles.
f. I want this config. to be a stepping stone in case the we decide to
connect to another ISP. Would another external router be required?
- Jennifer Mellone
router bgp jjj {this is ARIN registered ASN for the company}
network k.k.k.k {this is registered class B to be advertised}
network l.l.l.l {registered class C which will go away later; re-ip to the
class B}
neighbor a.a.a.a remote-as xxx {xxx ISP's ASN; a.a.a.a loopback of ISP's
router for 1st t1}
neighbor a.a.a.a ebgp-multihop
neighbor a.a.a.a update-source loopback0
neighbor b.b.b.b remote-as xxx {xxx ISP's ASN; b.b.b.b loopback of ISP's
router for 2nd t1}
neighbor b.b.b.b ebgp-multihop
neighbor b.b.b.b update-source loopback0
neighbor c.c.c.c remote-as xxx {xxx ISP's ASN; c.c.c.c loopback of ISP's
router for 3rd t1}
neighbor c.c.c.c ebgp-multihop
neighbor c.c.c.c update-source loopback0
neighbor d.d.d.d remote-as xxx {xxx ISP's ASN; d.d.d.d loopback of ISP's
router for 4th t1}
neighbor d.d.d.d ebgp-multihop
neighbor d.d.d.d update-source loopback0
neighbor e.e.e.e remote-as xxx {xxx ISP's ASN; e.e.e.e is the ISP's DS3
serial link address}
!
ip route 0.0.0.0 0.0.0.0 h.82.10.145 210 {ISP's serial link address for 1st
T1}
ip route 0.0.0.0 0.0.0.0 h.82.10.149 210 {ISP's serial link address for 2nd
T1}
ip route 0.0.0.0 0.0.0.0 h.82.10.153 210 {ISP's serial link address for 3rd
T1}
ip route 0.0.0.0 0.0.0.0 h.82.10.157 210 {ISP's serial link address for 4th
T1}
ip route 0.0.0.0 0.0.0.0 e.e.e.e 205 {e.e.e.e ISP's DS3 serial link; low
admin distance to prefer this path}
ip route k.k.k.k 255.255.0.0 k.k.k.4 {to get to the k.k.k.k class b stuff;
k.k.k.4 is the virtual IP for the 2 firewalls}
ip route l.l.l.l 255.255.255.0 1.1.1.16 {remove this 1.1.1.1 class c stuff
later}
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