Routing

Hello All, 

I  have some mix of juniper switches running MSTP. The switches are 4550/2300/3300 . we also have MX80 as router. its flat layer 2 network where all Gateways are defined on the mx and almost all clients use Mikrotik routers. all was well untill 3 days ago when some client routers just cant be reached from outside. if i ping the mikrotik from the MX where p2p GW is defined ..i can reach the mikrotik .. but if source the ping from the loopback IP of the same juniper router, i cant reach the client mikrotik. looks like mikrotiks just loose default GW for brief 10mins. some of them come back after 8mins...

this issue is eating my head. its just random IPs. some other clients are totaly fine.. at this rate i cant ping point the issue. i have reboot the mx and some behaved. i have noted rebooted any of the switches.. i am thinking of doing that in the next 4 hrs when there is no much traffic.

Any tips on what to check?

Attachment(s)

MSTP-DIAGRAM.drawio.pdf   54 KB 1 version

Are you using any dynamic protocols towards the Microtiks to announce the default gateway (OSPF, BGP, anything like that?)

As for rebooting the switches, while it's always possible to troubleshoot, I highly doubt they are involved. You are able to ping from the router's gateway so that means there is local layer 3 connectivity, meaning layer 2 and below are working fine unless you are running into a loadbalancing issue or something like that.

I do see there are 2 MX80s though. Are these doing any sort of redundancy protocol like VRRP or anything like that, or are these 2 separate devices with some clients having a gateway on the one router and some on the other? How is redundancy arranged?

Assuming both gateway routers are used for all clients (since there are different upstreams on both) you will need some sort of connectivity between the 2 routers to ensure that return packets arriving on router 1 can also get to router 2 if they need to reach a destination there and vice versa, so how is that set up?