ESR series service routers.ESR-Series. User manual
Step Description Command Keys
14 Enable key transmitting in GRE tunnel 
header (according to RFC 2890) and 
set the key value. Configured only on 
the both tunnel sides (optional).
esr(config-gre)# key <KEY> <KEY> – KEY value, takes 
values in the range of 
[1..2000000].
Default value: key is not 
transmitted.
15 Enable the calculation of the 
checksum and entry it to the GRE 
header of the packets to be sent. Also 
it is necessary to enable verifying of 
the checksum on the remote side 
(optional).
esr(config-gre)# local checksum
16 Enable verification of the presence 
and consistency of checksum values 
in the headers of GRE packets being 
received. Also it is necessary to 
enable calculation of the checksum on 
the remote side (optional).
esr(config-gre)# remote checksum
17 Enable the check for tunnel remote 
gateway availability (optional).
esr(config-gre)# keepalive enable
18 Change the keepalive packets timeout 
from the opposing party (optional).
esr(config-gre)# keepalive timeout 
<TIME>
<TIME> – time in seconds, 
takes values of [1..32767].
Default value: 10.
19 Change the number of attempts to 
check the availability of a tunnel 
remote gateway (optional).
esr(config-gre)# keepalive retries 
<VALUE>
<VALUE> – number of 
attempts, takes values in the 
range of [1..255].
Default value: 5.
20 Specify the IP address for the 
keepalive mechanism (mandatory in 
ethernet mode).
esr(config-gre)# keepalive dst-
address <ADDR>
<ADDR> – IP address to check 
GRE tunnel capability.
21 Change the time interval during which 
the statistics on the tunnel load is 
averaged (optional).
esr(config-gre)# load-average 
<TIME>
<TIME> – interval in seconds, 
takes values of [5..150].
Default value: 5.
22 Enable sending snmp-trap about 
tunnel enabling/disabling.
esr(config-gre)# snmp init-trap