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| -rw-r--r-- | docs/interfaces/tunnel.rst | 69 |
1 files changed, 65 insertions, 4 deletions
diff --git a/docs/interfaces/tunnel.rst b/docs/interfaces/tunnel.rst index 8fa1c0d7..1f191c16 100644 --- a/docs/interfaces/tunnel.rst +++ b/docs/interfaces/tunnel.rst @@ -6,9 +6,19 @@ Tunnel Interfaces Generic Routing Encapsulation (GRE) ----------------------------------- -A GRE tunnel requires a tunnel source (local-ip), a tunnel destination (remote-ip), +A GRE tunnel operates at layer 3 of the OSI model and is repsented by IP protocol 47. The +main benefit of a GRE tunnel is that you are able to route traffic across disparate networks. +GRE also supports multicast traffic and supports routing protocols that leverage multicast to +form neighbor adjacencies. + +Configuration +^^^^^^^^^^^^^ + +A basic configuration requires a tunnel source (local-ip), a tunnel destination (remote-ip), an encapsulation type (gre), and an address (ipv4/ipv6). Below is a configuration example -taken from a VyOS router and a Cisco IOS router. +taken from a VyOS router and a Cisco IOS router. The main difference between these two +configurations is that VyOS requires you explicitly configure the encapsulation type. +The Cisco router defaults to 'gre ip' otherwise it would have to be configured as well. **VyOS Router:** @@ -28,9 +38,60 @@ taken from a VyOS router and a Cisco IOS router. tunnel source 198.18.2.2 tunnel destination 198.18.0.2 -The main difference between these two configurations is that VyOS requires you explicitly -configure your encapsulation type. The Cisco router defaults to 'gre ip'. +Troubleshooting +^^^^^^^^^^^^^^^ + +GRE is a well defined standard that is common in most networks. While not inherently difficult +to configure there are a couple of things to keep in mind to make sure the configuration performs +as expected. A common cause for GRE tunnels to fail to come up correctly include ACL or Firewall +configurations that are discarding IP protocol 47 or blocking your source/desintation traffic. + +**1. Confirm IP connectivity between tunnel local-ip and remote-ip:** + +.. code-block:: sh + + vyos@vyos:~$ ping 198.18.2.2 interface 198.18.0.2 count 4 + PING 198.18.2.2 (198.18.2.2) from 198.18.0.2 : 56(84) bytes of data. + 64 bytes from 198.18.2.2: icmp_seq=1 ttl=254 time=0.807 ms + 64 bytes from 198.18.2.2: icmp_seq=2 ttl=254 time=1.50 ms + 64 bytes from 198.18.2.2: icmp_seq=3 ttl=254 time=0.624 ms + 64 bytes from 198.18.2.2: icmp_seq=4 ttl=254 time=1.41 ms + + --- 198.18.2.2 ping statistics --- + 4 packets transmitted, 4 received, 0% packet loss, time 3007ms + rtt min/avg/max/mdev = 0.624/1.087/1.509/0.381 ms + +**2. Confirm the link type has been set to GRE:** + +.. code-block:: sh + + vyos@vyos:~$ show interfaces tunnel tun100 + tun100@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1476 qdisc noqueue state UNKNOWN group default qlen 1000 + link/gre 198.18.0.2 peer 198.18.2.2 + inet 10.0.0.1/30 brd 10.0.0.3 scope global tun100 + valid_lft forever preferred_lft forever + inet6 fe80::5efe:c612:2/64 scope link + valid_lft forever preferred_lft forever + + RX: bytes packets errors dropped overrun mcast + 2183 27 0 0 0 0 + TX: bytes packets errors dropped carrier collisions + 836 9 0 0 0 0 + +**3. Confirm IP connectivity across the tunnel:** + +.. code-block:: sh + + vyos@vyos:~$ ping 10.0.0.2 interface 10.0.0.1 count 4 + PING 10.0.0.2 (10.0.0.2) from 10.0.0.1 : 56(84) bytes of data. + 64 bytes from 10.0.0.2: icmp_seq=1 ttl=255 time=1.05 ms + 64 bytes from 10.0.0.2: icmp_seq=2 ttl=255 time=1.88 ms + 64 bytes from 10.0.0.2: icmp_seq=3 ttl=255 time=1.98 ms + 64 bytes from 10.0.0.2: icmp_seq=4 ttl=255 time=1.98 ms + --- 10.0.0.2 ping statistics --- + 4 packets transmitted, 4 received, 0% packet loss, time 3008ms + rtt min/avg/max/mdev = 1.055/1.729/1.989/0.395 ms Virtual Tunnel Interface (VTI) ------------------------------ |