How to properly configure source routing on Ubuntu 18.04?

Ben N

12/9/22, 1:23 PM

I'm trying to configure a new VLAN/Subnet on my Ubuntu 18.04 servers. I'm trying to follow the example here: https://netplan.io/examples/#configuring-source-routing

But when I follow that example, I can SSH into the servers via the br10 interface address. But from there, I can't ssh to the other nodes via either the br10 or br11 interface. Additionally, the Kubernetes cluster running on the Servers can no longer communicate with the other components. The problem that I'm trying to solve is that when users connect to a service running on the br11 interface, the response packet is going out over the br10/VLAN10 interface and being dropped by the network.

Here is my netplan configuration:

network:
version: 2
renderer: networkd

ethernets:
  eth0:
    addresses: []
    dhcp4: false
    dhcp6: false
  eth1:
    addresses: []
    dhcp4: false
    dhcp6: false

bonds:
  bond0:
    interfaces:
      - eth0
      - eth1
    dhcp4: false
    dhcp6: false
    parameters:
      lacp-rate: fast
      mii-monitor-interval: 100
      mode: 802.3ad

vlans:
  vlan10:
    id: 10
    link: bond0
    dhcp4: false
    dhcp6: false
  vlan11:
    id: 11
    link: bond0
    dhcp4: false
    dhcp6: false

bridges:
  br10:
    interfaces:
      - vlan10
    addresses:
      - 10.0.10.2/24
    nameservers:
    addresses:
      - 10.0.1.1
      - 10.0.1.2
    search:
      - domain.com
    dhcp4: false
    dhcp6: false
    routes:
      - to: 0.0.0.0/0
        via: 10.0.10.1
      - to: 10.0.10.0/24
        via: 10.0.10.1
        table: 10
    routing-policy:
      - from: 10.0.10.0/24
        table: 10
   
  br11:
    interfaces:
      - vlan11
    addresses:
      - 10.0.11.2/24        
    nameservers:
    addresses:
      - 10.0.1.1
      - 10.0.1.2
    search:
      - domain.com
    dhcp4: false
    dhcp6: false
    routes:
      - to: 10.0.11.0/24
        via: 10.0.11.1
        table: 11
    routing-policy:
      - from: 10.0.11.0/24
        table: 11

What am I doing wrong? What's the "right" way to do ensure response packets are routed out the same interface that they arrived on?

Thanks!

386

2 + 0

netplan

18.04

Score:0

Ubuntu

Ben N

12/13/22, 2:51 PM

I did finally work out my issue and it turned out that I was hitting the corporate firewall in a way that I didn't expect. My final netplan in case it's helpful to someone in the future looks like:

network:
  version: 2
  renderer: networkd
  
  ethernets:
    eth0:
      addresses: []
      dhcp4: false
      dhcp6: false

  bonds:
    bond0:
      interfaces:
        - eth0
      dhcp4: false
      dhcp6: false
      parameters:
        lacp-rate: fast
        mii-monitor-interval: 100
        mode: 802.3ad
  
  vlans:
    vlan10:
      id: 10
      link: bond0
      dhcp4: false
      dhcp6: false
      addresses:
        - 10.0.10.2/24
      gateway4: 10.0.10.1
      nameservers:
        addresses:
          - 10.0.1.1
          - 10.0.1.2
        search:
          - domain.com
      dhcp4: false
      dhcp6: false

    vlan11:
      id: 11
      link: bond0
      dhcp4: false
      dhcp6: false
      addresses:
        - 10.0.11.2/24
      nameservers:
        addresses:
          - 10.0.1.1
          - 10.0.1.2
        search:
          - domain.com
      dhcp4: false
      dhcp6: false
      routes:
        - to: 0.0.0.0/0
          via: 10.0.11.1
          metric: 11       
        - to: 0.0.0.0/0
          via: 10.0.11.1
          table: 11
        - to: 10.0.11.0/24
          via: 10.0.11.1
          table: 11
      routing-policy:
        - from: 10.0.11.0/24
          table: 11

I did end up adding a default route to my alternate table as @slangasek suggested.

0 + 0

Score:0

Ubuntu

slangasek

12/10/22, 7:07 PM

Your routing table doesn't show any routes for the br11 interface except for the local network, which doesn't require the use of routing policies anyway. You probably are missing a default route (0.0.0.0/0) for the br11 interface as part of the source routing policy.

0 + 0

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: How to properly configure source routing on Ubuntu 18.04?

TH: จะกำหนดค่าการกำหนดเส้นทางต้นทางบน Ubuntu 18.04 ได้อย่างไร

RO: Cum se configurează corect rutarea sursei pe Ubuntu 18.04?

RU: Как правильно настроить исходную маршрутизацию в Ubuntu 18.04?

VI: Làm cách nào để định cấu hình đúng định tuyến nguồn trên Ubuntu 18.04?

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