How to change time interval for ARP to hold info in its cache?

[henk van dorp]

Hi there,

Does someone know to set the time interval for ARP to hold info in its cache on a OpenVMS 7.3-2 system running TCPIP V5.4 ECO 6?

(well: RTFM is a possible answer :>P )

In the TCPIP-manual (Tuning and troubleshooting) in chapter 1.2.3 a command as
$ SET [CONFIG] PROTOCOL ARP is mentioned and referred to in the Command Reference.....

But neither the command reference nor DCL HELP recognizes this command.

Anybody a clue?

thnx in advance

Henk van Dorp

[Wim Van den Wyngaert · Accepted solution]

I agree that it's a mess.

Check the arp command (arp -?) and the unix doc.

Or use "sysconfig -q net" to see them.

arpkillc : sec after which a completed arp timeouts. Not sure that it's this but the value 1200 on my system is 20 minutes which is the default timeout.

Wim

[henk van dorp]

Wim,

thanks for your answer. It is what I've experienced to (20 minute to timeout).

with regards

Henk

[henk van dorp]

Wim,
your answer pointed me to the solution.
I pick it up from here. thanx

But....

after modifying the sysconfigtab with sysconfigdb, nothing changed in behaviour.

AX0172[DORPH]tcpip sysconfig -q net
net:
arpkillc = 30
arpkilli = 180
arprefresh = 120
arpunicast = 1
ifqmaxlen = 1024
lo_devs = 1
lo_def_ip_mtu = 4096
nslip = 0
ovms_unit_count = 27
ovms_unit_creates = 638
ovms_unit_fast_credel = 0
ovms_unit_limit = 9998
ovms_unit_minimum = 2
ovms_unit_maximum = 9999
ovms_unit_seed = 637

and:

AX0172[DORPH]typ tcpip$etc:sysconfigtab.dat
#
# TCP/IP Services for OpenVMS V5.1
# sysconfig parameter file
#
nfs:
tcp_threads=8
udp_threads=8

vfs:
vnode_age=120

inet:
tcp_keepalive_default=1
tcp_keepidle=150

net:
arpkillc=30

Restarting TCPIP didn't change the duration, nor did a reboot.

Do I forget something?

with regards

Henk

[Wim Van den Wyngaert]

(but I was wrong on arp, that's the equiv of ucx sho arp)

Wim

[Wim Van den Wyngaert]

With ucx sho arp you can see the timer associated with each arp entry. It seems indeed that it gets refreshed each time. Could it be that the refresh timer must be bigger than the killc ?

Found nothing with google !

Wim

[Wim Van den Wyngaert]

Did some testing on ucx 5.3.

The arpkillc works as expected. An unsed connection (or in use but no packets are sent/received) times out and is removed after x seconds. Each time the connection is used, the timer is reset (just type return in a telnet).

If I change it to 30 seconds, it's removed after 30. Works fine.

But then I tried arprefresh. Based upon muy tests this seems to be the time after which an in use but not active entry is refreshed but not in seconds (as documented) but in MINUTES.

If I put it on 1, the in-active, inuse arp entry is refreshed every minute.

As soon as it finished being used, the arpkillc becomes active again.

The arpkili seems to be used when you use an IP address that is not in use. Nobody responds and the arp entry (with no hw address is kept in the cache for arpkili seconds (I=incomplete).

Hope this helps. It did in any case update my knowledge of arp.

Wim

[henk van dorp]

Wim,

Thanks for your tests.
Finally I detected that ARP was not routable... That solved my struggle that my pc did not reach the arp-table

still learning ;>)

Henk

[henk van dorp]

Wim,
thanks for your help.

Henk