If I'm not misinterpreting the routing table below, the customer won't be able to communicate with the "Bandung Institute of Technology" because the gateway has a local route.
But anyway, the SK provided by Chris will help.
Maybe someone at R&D can have a look at this issue, perhaps shifting internal communications to a separate network namespace could do the trick.
Thanks a lot for your help!
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Routing table from customer SMO:
[Expert@firewall-ch01-01:0]# ip route show
default via x.x.x.x dev magg0 proto 7
x.x.x.x/24 dev bond1.x proto kernel scope link src x.x.x.x
x.x.x.x/24 dev magg0 proto kernel scope link src x.x.x.x
192.0.2.0/24 dev Sync proto kernel scope link src 192.0.2.1
198.51.101.0/25 dev eth1-CIN proto kernel scope link src 198.51.101.1
198.51.101.128/25 dev eth2-CIN proto kernel scope link src 198.51.101.201