[c-nsp] GRE tunnel 8000kbit (8Mbit) limit issue

[A.L.M.Buxey at lboro.ac.uk]

hi,

okay...have googled and looked around...and no current joy.


we have a GRE tunnel between a 6506 (sup2T) running IOS 15.1 and a 3750 running IOS 15.2

both ends report the tunnel interface as having the following details/limits

  Tunnel TTL 255, Fast tunneling enabled
  Path MTU Discovery, ager 10 mins, min MTU 92
  Tunnel transport MTU 1476 bytes
  Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps)

note, this isnt the 'bandwidth' used for graphs...thats configurable up to 40GBit...being a 1Gig physical link we've set that to 1000000kbit (1000mbit - 1Gbit)


according to docs (and internet searches....)there was an old command to set  tunnel bandwidth receive and send.... was in 12.2/3 but removed in 12.4 or such...and
we're running 15.1 and 15.2  - also, the command was only in adv ip services.... which is what we're running on the 6500 end...   ipservices on the 3750x (can that
even run adv ip services? when i run the licence command to change it , theres only ipservice, ipbase and lanbase as options!)..but anyway, cant even set at
one end..let alone the other.

running eg iperf/iperf3 through this GRE we get 7.97mbit - pretty much spot on to that limit.... more interesting..and to concur with other posts I've read,
if we set up a tunnel between 2 6500 (same platform...) we can get higher speeds with no problem.... so the limit is in config/template/default....but its not
cared about by the sup2T !!  it seems it is adhered to by the 3750x though   :(

so, since Cisco are always going on about using GRE for site to site links encapsulated in an IPSec tunnel so that you can do dynamic routing protocols etc...
well.. this remote site is 3750x and at 8mbit top speed i dont think so!!   - any clues as to whether I can get this sorted or is there some limit in the platform
that I should worry about anyway...or some cisco secret command to change that value?  


many thanks

alan