IP Fabric
Next topic – Layer 3 Underlay – Clos IP fabric.
Please refer to Juniper QFX5100 Series book and this whitepaper.
Pretty basic stuff if you already have some experience with BGP and policies.
Make sure you know the differences between various IBGP and EBGP design options, although there is only EBGP option stated explicitly in JNCIE-DC lab exam topics. Learn different schemas of AS numbers assignment.
BGP configuration example:
bgp {
log-updown;
import bgp-clos-in;
export bgp-clos-out;
graceful-restart;
group CLOS {
type external;
mtu-discovery;
bfd-liveness-detection {
minimum-interval 350;
multiplier 3;
session-mode single-hop;
}
multipath multiple-as;
neighbor 192.168.0.1 {
peer-as 200;
}
neighbor 192.168.0.3 {
peer-as 201;
}
neighbor 192.168.0.5 {
peer-as 202;
}
}
}
log-updown;
import bgp-clos-in;
export bgp-clos-out;
graceful-restart;
group CLOS {
type external;
mtu-discovery;
bfd-liveness-detection {
minimum-interval 350;
multiplier 3;
session-mode single-hop;
}
multipath multiple-as;
neighbor 192.168.0.1 {
peer-as 200;
}
neighbor 192.168.0.3 {
peer-as 201;
}
neighbor 192.168.0.5 {
peer-as 202;
}
}
}
Important things to note here are multipath multiple-as statement and BFD session-mode single-hop configuration.
Export policy:
policy-statement bgp-clos-out {
term loopback {
from {
protocol direct;
route-filter 10.0.0.0/24 orlonger;
}
then {
next-hop self;
accept;
}
}
term server-L3-gw {
from {
protocol direct;
route-filter 172.16.0.0/12 orlonger;
}
then {
next-hop self;
accept;
}
}
}
term loopback {
from {
protocol direct;
route-filter 10.0.0.0/24 orlonger;
}
then {
next-hop self;
accept;
}
}
term server-L3-gw {
from {
protocol direct;
route-filter 172.16.0.0/12 orlonger;
}
then {
next-hop self;
accept;
}
}
}
And import policy:
policy-statement bgp-clos-in {
term loopbacks {
from {
route-filter 10.0.0.0/24 orlonger;
}
then accept;
}
term server-L3-gw {
from {
route-filter 172.16.0.0/12 orlonger;
}
then accept;
}
term reject {
then reject;
}
}
term loopbacks {
from {
route-filter 10.0.0.0/24 orlonger;
}
then accept;
}
term server-L3-gw {
from {
route-filter 172.16.0.0/12 orlonger;
}
then accept;
}
term reject {
then reject;
}
}
This config is pretty self-explanatory, if you need some clarification please refer to this Clos IP Fabrics whitepaper.