2 ISP fail over with juniper SRX

We have two ISPs, ISP A and ISP B.
What we want to accomplish is, if primary ISP’s link fail, then switch the link through secondary link to ISP B. So, let’s get started.



We need to configure the routing table under [routing-options] hierarchy.

[edit routing-options]

 

user@SRX240# set static route 0.0.0.0/0 next-hop 1.1.1.1 preference 5 [Next hop 1.1.1.1 is the primary next-hop for 0.0.0.0/0 destination network. Note, 0.0.0.0/0 means default gateway. Preference 5 is the default preference for static routes. Even if you don’t put preference 5 in this command, it is automatically there.

 

[edit routing-options]

user@SRX240# set static route 0.0.0.0/0 qualified-next-hop 2.2.2.1 preference 7 [Now next-hop 2.2.2.1 is the secondary next-hop for 0.0.0.0/0 network. It has the preference of 7. If the primary link is to go down, this link will be the gateway for the default route.

[edit routing-options]

user@SRX240# show

static {

route 0.0.0.0/0 {

next-hop 1.1.1.1;

qualified-next-hop 2.2.2.1 {

preference 7;

}

preference 5;

}

}