Arista EOS Tunneling Mechanism (2) - Hw/Sw Tunnel

We first talk a bit on GRE tunneling - "tunnel interface".

• Starting from 4.17.0F, you can configure a software GRE tunnel with ISIS over it. 
• Over the tunnel, it is ONLY for the control plane as specified in the feature limitation
• "The only supported use case is to allow IS-IS on the switch to advertise its routes over a GRE tunnel to a remote system that hosts IS-IS topology-learning applications."  
• So it is more like to establish isis neighbor and advertise ISIS LSDB to remote software. 
• In 4.21.1F, the hardware GRE tunnel is supported on Jericho platforms like 7280R, 7500R and 7020R. But as of now (Jun 2019), only supported overlay routing protocol is BGP/ISIS. 

Here is the detailed comparison between 2 types of tunnel interfaces:

Some configuration tips:

• The configuration is same, the system will automatically select hardware or software based on hardware platform and release. 
• "show interface tunnel #" shows the tunnel type. Please note that even this show interface output indicates the interface is up, it doesn't mean it is working. Better to verify by ping the tunnel interaface ip address. 
• Only GRE mode is supported, even there is other options like ipip or Ipsec in the CLI. 
• Underlay endpoint address family, only the ipv4 is supported, even there is options like "tunnel source/dest <ipv6Adr>"