Help Configuring a Network Adapter on VE Host

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greenhornet

New Member
Jan 31, 2025
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I've got several adapter cards on my Proxmox server. They're all showing up in the datacenter server view under my host server in the network settings. That much is good. The first NIC is getting an IP address from the DHCP server but the second is not. I've got a total of 6 NICs on this server. Two of them are plugged in and show physical link lights on the cards. Of those two, one is not getting an IP address.
I have two challenges:
1. How to identify the card in Proxmox that has a cabled connection and link (but no IP) and then
2. How to configure that adapter to accept DHCP.
Proxmox NICs.png
 
Hi,

greenhornet said:
The first NIC is getting an IP address from the DHCP server but the second is not.
Click to expand...
DHCP is only used during installation, that received address is than set as static address.
On an installed system, no DHCP is performed on any host network interfaces - since in such environments, you'd rarely want that anyway and isn't really supported.
Changing IP address is not trivial on Proxmox VE, since you need to take care of a few sites to match everything up.

If you are really sure you want to use DHCP, see the Debian documentation: https://wiki.debian.org/NetworkConfiguration#Using_DHCP_to_automatically_configure_the_interface
 
cheiss said:
Hi,


DHCP is only used during installation, that received address is than set as static address.
On an installed system, no DHCP is performed on any host network interfaces - since in such environments, you'd rarely want that anyway and isn't really supported.
Changing IP address is not trivial on Proxmox VE, since you need to take care of a few sites to match everything up.

If you are really sure you want to use DHCP, see the Debian documentation: https://wiki.debian.org/NetworkConfiguration#Using_DHCP_to_automatically_configure_the_interface
Click to expand...
Thanks. Static is definitely fine - but I'm still trying to solve #1 - how can I tell which one of those cards has the connection if we can't use DHCP first?
 
greenhornet said:
how can I tell which one of those cards has the connection
Click to expand...
You can use e.g. ip link on the shell, which lists all network interfaces with their flags/operational stats.
NO-CARRIER means that no cable is plugged in, while LOWER_UP indicates a physical connection. UP indicates administratively up.

For further information, you can also use ethtool <portname>, which lists, among other things, available/negotiated speed.
 
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cheiss said:
You can use e.g. ip link on the shell, which lists all network interfaces with their flags/operational stats.
NO-CARRIER means that no cable is plugged in, while LOWER_UP indicates a physical connection. UP indicates administratively up.

For further information, you can also use ethtool <portname>, which lists, among other things, available/negotiated speed.
Click to expand...
If I'm reading my output (below) corectly, the system only thinks I have 1 interface with a cable connected. I have visually verified that both cables are plugged in and have link lights on their respective ports - at the NIC.

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp3s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master vmbr0 state UP mode DEFAULT group defaul t qlen 1000
link/ether 9c:8e:99:0f:be:24 brd ff:ff:ff:ff:ff:ff
3: enp3s0f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 9c:8e:99:0f:be:26 brd ff:ff:ff:ff:ff:ff
4: enp4s0f0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 9c:8e:99:0f:be:28 brd ff:ff:ff:ff:ff:ff
5: enp4s0f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 9c:8e:99:0f:be:2a brd ff:ff:ff:ff:ff:ff
6: ens3f0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether a0:36:9f:37:d2:b4 brd ff:ff:ff:ff:ff:ff
altname enp14s0f0
7: ens3f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether a0:36:9f:37:d2:b6 brd ff:ff:ff:ff:ff:ff
altname enp14s0f1
8: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
link/ether 9c:8e:99:0f:be:24 brd ff:ff:ff:ff:ff:ff

It should be one of these two, because it's a 10GbE card and both show 10000baseT (the other card is only 1000). The "link detected" is what's throwing me.
root@jayne:~# ethtool ens3f0
Settings for ens3f0:
Supported ports: [ TP ]
Supported link modes: 100baseT/Full
1000baseT/Full
10000baseT/Full
Supported pause frame use: Symmetric
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 100baseT/Full
1000baseT/Full
10000baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: Unknown!
Duplex: Unknown! (255)
Auto-negotiation: on
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
MDI-X: Unknown
Supports Wake-on: d
Wake-on: d
Current message level: 0x00000007 (7)
drv probe link
Link detected: no



root@jayne:~# ethtool ens3f1
Settings for ens3f1:
Supported ports: [ TP ]
Supported link modes: 100baseT/Full
1000baseT/Full
10000baseT/Full
Supported pause frame use: Symmetric
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 100baseT/Full
1000baseT/Full
10000baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: Unknown!
Duplex: Unknown! (255)
Auto-negotiation: on
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
MDI-X: Unknown
Supports Wake-on: d
Wake-on: d
Current message level: 0x00000007 (7)
drv probe link
Link detected: no


If I move the same cable to any other port (of the 5 available NICs) I get the same result. Link light is on but the ip link command shows everything down except the one I configured at installation.
 
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