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====== Filter Out Unwanted Interfaces Using Grep ======
<color #db5f0b>Nov 2023</color>
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When using Linux with Docker/Containers there can be a lot of virtual interfaces, while this is not a problem itself, listing just the physical interfaces can be.
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For example, if we do an '<color #ed1c24>ip -br -c a</color>' we can get quite a list:
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<file>
lo               UNKNOWN        127.0.0.1/8
eno1             UP             10.32.13.233/24
eno2             UP             11.0.233.2/16
eno3             UP             12.0.233.3/16
eno4             DOWN
internalk3s0     UNKNOWN        192.168.255.1/24
kube-ipvs0       DOWN           10.43.121.13/32 10.43.139.106/32 10.43.41.193/32 10.43.199.244/32 10.43.0.10/32 10.43.88.3/32 10.43.25.131/32 10.43.120.24/32 10.43.39.71/32 10.43.212.213/32 192.168.255.1/32 10.43.41.212/32 10.43.206.154/32 10.43.148.235/32 10.43.26.88/32 10.43.217.244/32 10.43.79.27/32 10.43.115.178/32 10.43.114.120/32 10.43.66.108/32 10.43.44.118/32 10.43.136.197/32 10.43.127.60/32 10.43.138.232/32 10.43.54.183/32 10.43.110.33/32 10.43.0.1/32 10.43.60.91/32 10.43.19.143/32 10.43.123.229/32 10.43.21.162/32 10.43.92.123/32 10.43.220.178/32 10.43.87.169/32 10.43.159.224/32 10.43.18.24/32 10.43.47.137/32 10.43.24.141/32 10.43.236.14/32 10.43.17.91/32 10.43.182.233/32 10.43.195.135/32 10.43.192.38/32 10.43.157.8/32 10.43.137.179/32 10.43.196.255/32 10.43.158.51/32 10.43.23.5/32
flannel.1        UNKNOWN        10.42.0.0/32
cni0             UP             10.42.0.1/24
veth3d27dfa7@if2 UP
vethb0a17eb4@if2 UP
veth619f3a08@if2 UP
veth0977d0fb@if2 UP
vethe60bc71c@if2 UP
veth8a69f3b6@if2 UP
veth1437d366@if2 UP
veth3a247e74@if2 UP
vethc8654bec@if2 UP
veth62cbba67@if2 UP
vethfd3f5763@if2 UP
vethdd5adce6@if2 UP
veth567a8f8d@if2 UP
veth0b064639@if2 UP
vethdeed99b2@if2 UP
veth04829d3b@if2 UP
veth6660a31c@if2 UP
veth2c06a596@if2 UP
veth99db8892@if2 UP
veth47ce8ea5@if2 UP
veth976d6e7f@if2 UP
vethe4ae5d10@if2 UP
veth6c7cd23e@if2 UP
veth71d280a4@if2 UP
vethd227b1f6@if2 UP
veth55a1c60b@if2 UP
vethbc6f5ccc@if2 UP
vethc25d04a7@if2 UP
veth93d06e97@if2 UP
veth2641a619@if2 UP
veth284b1fa0@if2 UP
vethe1fdb3e7@if2 UP
veth905c6a4e@if2 UP
vethd1853059@if2 UP
veth0a79a49b@if2 UP
veth48b4b040@if2 UP
veth1ac96caa@if2 UP
veth3f9ad283@if2 UP
vethef6fb521@if2 UP
vethaacee777@if2 UP
vetha6ac44b4@if2 UP
veth05123eed@if2 UP
veth91566343@if2 UP
veth0f16c600@if2 UP
</file>
This may or may not be an issue, but sometimes this long list means the interfaces you are interested in will scroll off the top of the page. You could use something like head:
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<color #ed1c24>ip -br -c a | head</color>
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This will give an output similar to:
<file>
lo               UNKNOWN        127.0.0.1/8
eno1             UP             10.32.13.233/24
eno2             UP             11.0.233.2/16
eno3             UP             12.0.233.3/16
eno4             DOWN
internalk3s0     UNKNOWN        192.168.255.1/24
kube-ipvs0       DOWN           10.43.121.13/32 10.43.139.106/32 10.43.41.193/32 10.43.199.244/32 10.43.0.10/32 10.43.88.3/32 10.43.25.131/32 10.43.120.24/32 10.43.39.71/32 10.43.212.213/32 192.168.255.1/32 10.43.41.212/32 10.43.206.154/32 10.43.148.235/32 10.43.26.88/32 10.43.217.244/32 10.43.79.27/32 10.43.115.178/32 10.43.114.120/32 10.43.66.108/32 10.43.44.118/32 10.43.136.197/32 10.43.127.60/32 10.43.138.232/32 10.43.54.183/32 10.43.110.33/32 10.43.0.1/32 10.43.60.91/32 10.43.19.143/32 10.43.123.229/32 10.43.21.162/32 10.43.92.123/32 10.43.220.178/32 10.43.87.169/32 10.43.159.224/32 10.43.18.24/32 10.43.47.137/32 10.43.24.141/32 10.43.236.14/32 10.43.17.91/32 10.43.182.233/32 10.43.195.135/32 10.43.192.38/32 10.43.157.8/32 10.43.137.179/32 10.43.196.255/32 10.43.158.51/32 10.43.23.5/32
flannel.1        UNKNOWN        10.42.0.0/32
cni0             UP             10.42.0.1/24
veth3d27dfa7@if2 UP
</file>
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However, we can use GREP to filter out the unwanted entries, in this example the biggest number of unwanted entries are the 'vethxxxxxxxx' entries, we can filter these out using the following (because they all contain 'veth')
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<color #ed1c24>ip -br -c a |grep -v veth</color>
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<file>
lo               UNKNOWN        127.0.0.1/8
eno1             UP             10.32.13.233/24
eno2             UP             11.0.233.2/16
eno3             UP             12.0.233.3/16
eno4             DOWN
internalk3s0     UNKNOWN        192.168.255.1/24
kube-ipvs0       DOWN           10.43.121.13/32 10.43.139.106/32 10.43.41.193/32 10.43.199.244/32 10.43.0.10/32 10.43.88.3/32 10.43.25.131/32 10.43.120.24/32 10.43.39.71/32 10.43.212.213/32 192.168.255.1/32 10.43.41.212/32 10.43.206.154/32 10.43.148.235/32 10.43.26.88/32 10.43.217.244/32 10.43.79.27/32 10.43.115.178/32 10.43.114.120/32 10.43.66.108/32 10.43.44.118/32 10.43.136.197/32 10.43.127.60/32 10.43.138.232/32 10.43.54.183/32 10.43.110.33/32 10.43.0.1/32 10.43.60.91/32 10.43.19.143/32 10.43.123.229/32 10.43.21.162/32 10.43.92.123/32 10.43.220.178/32 10.43.87.169/32 10.43.159.224/32 10.43.18.24/32 10.43.47.137/32 10.43.24.141/32 10.43.236.14/32 10.43.17.91/32 10.43.182.233/32 10.43.195.135/32 10.43.192.38/32 10.43.157.8/32 10.43.137.179/32 10.43.196.255/32 10.43.158.51/32 10.43.23.5/32
flannel.1        UNKNOWN        10.42.0.0/32
cni0             UP             10.42.0.1/24
</file>
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If we wish to go further, we can filter out the kube/flannel/cnio etc by adding these to our command.
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<color #ed1c24>ip -br -c a |grep -v kube |grep -v veth |grep -v internal |grep -v flannel |grep -v cni0</color>
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This will give us a list of just the physical interfaces:
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<file>
lo               UNKNOWN        127.0.0.1/8
eno1             UP             10.32.13.233/24
eno2             UP             11.0.233.2/16
eno3             UP             12.0.233.3/16
eno4             DOWN
</file>
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