Understanding interface naming and mapping

asked 2019-01-30 03:31:47 -0600

anonymous user

Anonymous

Hello,

Having trouble to track interface naming convention and understanding what is connected with what.
For example:
20: tap9883a33b-93@if2: <broadcast,multicast,up,lower_up> mtu 1450 qdisc noqueue master brq77269583-11 state UP group default qlen 1000
21: vxlan-100: <broadcast,multicast,up,lower_up> mtu 1450 qdisc noqueue master brq77269583-11 state UNKNOWN group default qlen 1000
22: brq77269583-11: <broadcast,multicast,up,lower_up> mtu 1450 qdisc noqueue state UP group default qlen 1000
23: tapb6182aac-d9@if4: <broadcast,multicast,up,lower_up> mtu 1450 qdisc noqueue master brq77269583-11 state UP group default qlen 1000

Are all of these interfaces part of linux bridge brq77269583-11?
Is there any convention for naming of bridges and tap interfaces? What does @if2(4) means? How to trace what is connected with what? (what tap interface is connected with vxlan interface etc..)

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answered 2019-01-30 04:52:02 -0600

tap9883a33b-93@if2 belongs to a Neutron port with ID 9883a33b-93...

The if2 part means that the tap interface is one side of a veth pair, and interface number 2 is the other side. The other side resides in a router or dhcp namespace, and the abovementioned port represents a router interface or the connection point of a DHCP server.

brq77269583-11 is a Linux bridge that implements a VXLAN-based tenant network. 77269583-11.... is probably the network ID.

To better understand the plumbing, see the diagrams in the networking guide https://docs.openstack.org/neutron/la.... The page also contains traffic flow examples.

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I can see that this VXLAN is part of the linux bridge for demo_private_network in my case, but I can't identify to what underlying interface is this VXLAN connected. Any idea how to conclude that?

SavicNedovic gravatar imageSavicNedovic ( 2019-01-31 03:23:49 -0600 )edit

In the diagram, it's "interface 3". I don't know much about VXLAN, but according to the kernel docu, this command shows the details:

ip -d link show vxlan
Bernd Bausch gravatar imageBernd Bausch ( 2019-01-31 03:38:04 -0600 )edit

Tahnks again!

SavicNedovic gravatar imageSavicNedovic ( 2019-01-31 03:51:37 -0600 )edit
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answered 2019-01-31 01:59:16 -0600

SavicNedovic gravatar image

Thanks for explanation! I already studied packet flows that you sent and wanted to see that in practical example (in my test environment).
I understood how tap interfaces are named , and how veth pairs are defined. I found in one of the namespaces for DHCP corresponding veth pair ns-9883a33b-93@if20. I am still missing the part how is VXLAN interface from linux bridge mapped to corresponding underlying interface.
Example: vxlan-100: <broadcast,multicast,up,lower_up> mtu 1450 qdisc noqueue master brq77269583-11 state UNKNOWN group default qlen 1000 ; link/ether 4e:a4:94:43:c6:89 brd ff:ff:ff:ff:ff:ff network: 77269583-11c5-441c-a171-e1f331bc610a | demo_private_network | d8a18d2a-f667-4e34-9fa8-afe885b666b4

I can see that this VXLAN is part of the linux bridge for demo_private_network in my case, but I can't identify to what underlying interface is this VXLAN connected. Any idea how to conclude that?

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Asked: 2019-01-30 03:31:47 -0600

Seen: 297 times

Last updated: Jan 30 '19