MX1 -------- SwitchA --------- ISP A
MX2 ---------Switch B----------ISP B
x.x.x.0/24 Public IP subnet advertised to ISP A and ISP B.
eBGP with on MX1 and MX2 with both ISP A and ISP B.
For upstream traffic, ISP A is preferred one. (Using local pref when importing the default route from ISP A and ISP B)
We are planning to upgrade switches, which requires reboot on SwitchA and Switch B.
Upstream traffic can be manually failed over to ISP B using local pref. However, not sure about the downstream traffic.
What if ISP A will keep on getting replies even though it is down?
does BGP hold timer applies when interface goes down due to reboot?
What kind of downtime can be expected in this scenario?
if this is planned outage try to disable ISP A peer , then reboot switch , and enable ISPA again. After disabling peer bgp session will go down immediatly and all trafffic will be forwarded over ISP B