User guide

set tcpip
214 Chapter 2 Command Descriptions
set tcpip
Device support This command is supported in all devices.
Purpose Configures or displays operating characteristics of the Transmission
Control Protocol (TCP) for the Digi device, including the TCP port used by
RealPort, the interval TCP waits before retransmitting an unacknowledged
segment, how TCP handles idle connections, and socket service values for
reverse Telnet connections. The command options “garp” and “rto_min”
can be used to optimize for latency.
Required
permissions
The root user can configure TCP/IP settings. Normal users can display
TCP/IP settings.
Syntax Configure or change TCP options
set tcpip [arp_ttl=30-1200]
[garp=30-3600]
[ip_ttl=hops]
[keepalive_active={on|off}]
[keepalive_byte={on|off}]
[keepalive_idle=hours:minutes:seconds]
[probe_count=probe count#]
[probe_interval=probe interval#]
[rto_min=30-1000]
[rto_max=1-240]
[tcp_ttl=hops]
Display TCP settings
set tcpip
Options arp_ttl=30-1200
The initial value of the ARP time-to-live variable. When an ARP cache
entry first populated, the ARP time-to-live variable is set to this value.
When the entry has existed in the table for this long without being
updated, another ARP cache request is performed to make sure that
there is not a new a new device at that IP.
garp=30-3600
The frequency of Gratuitous ARP (GARP) announcements. A
Gratuitous ARP is a broadcast announcement to the network of a
device’s MAC address and the IP address being used for it. This
allows the network to update its ARP cache tables without performing
an ARP request on the network.
Gratuitous ARP announcements can affect latency in a limited way,
because some systems stall or dispose of data that is transmitted
during an ARP cache refresh. If this happens, setting the
Gratuitous ARP frequency to be more often than the problem system’s
time-to-live variable can cause it to refresh the cache without needing
to perform a request.