bond interface answering for another one

by Jure   Last Updated May 15, 2019 17:00 PM - source

I have a ubuntu 18 server with 4 active NICs. The setup is:
1. one public (not relevant for this case)
2. one single eno1 with ip 10.123.10.21
3. one bond0 (LACP bond consisting of eno3 and eno4), ip 10.123.10.30

2/eno1 & 3/bond0 are in the same network/vlan as bond0 is supposed to handle application traffic and eno1 is for mgmt and supporting services..

When enabling firewall (ufw) for some services on eno1 nothing seemed to work and after extensive digging and tcpdumping I figured out that bond0 is answering to arp requests for eno1 and all traffic goes to bond0 instead. And as long as the fw rules are not IP specific, things work but when you say allow to IP on IF nothing gets trough as this IP is actually being served by another IF.

I don't have ip forwarding on or any bridging

# cat /proc/sys/net/ipv4/ip_forward
0

On the switch side this VLAN is access only/untagged for internal traffic only, one LACP group for the bond0, the rest are standard. It is also ufw/iptables independent as I turned the service off and it stays the same (I thought it could be some pre-routing chain).

So I'm quite confused as to what's going on. I don't know what I could post to be useful. ip addr + routes seem ok:

2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 94:18:82:7b:9a:6c brd ff:ff:ff:ff:ff:ff
    inet 10.123.10.21/24 brd 10.123.10.255 scope global eno1
       valid_lft forever preferred_lft forever
4: eno3: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 9000 qdisc mq master bond0 state UP group default qlen 1000
    link/ether 2a:08:3c:37:0d:3a brd ff:ff:ff:ff:ff:ff
5: eno4: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 9000 qdisc mq master bond0 state UP group default qlen 1000
    link/ether 2a:08:3c:37:0d:3a brd ff:ff:ff:ff:ff:ff
8: bond0: <BROADCAST,MASTER,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
    link/ether 2a:08:3c:37:0d:3a brd ff:ff:ff:ff:ff:ff
    inet 10.123.10.30/24 brd 10.123.10.255 scope global bond0
       valid_lft forever preferred_lft forever
    inet6 fe80::2808:3cff:fe37:d3a/64 scope link 
       valid_lft forever preferred_lft forever
# ip r
default via ... dev eno50 proto static 
10.123.10.0/24 dev bond0 proto kernel scope link src 10.123.10.30 
10.123.10.0/24 dev eno1 proto kernel scope link src 10.123.10.21 
.../28 dev eno50 proto kernel scope link src .... 

If anyone has any ideas on where to move on from here I'd be grateful..

Jure



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