IBM Switch 9077 - Manual (Page 130)

112 IBM 9077 SP Switch Router: Get Connected to the SP Switch
VPIs 0 through 15 are available for configuration use. VPIs are assigned in
the /etc/gratm.conf file with regard to their VCI.
VCIs
VCIs name VCs. VCIs are also assigned in the /etc/gratm.conf file. On VPI 0,
VCI 0 through VCI 32767 can be used; on VPIs 1-15, VCI 0 through VCI 511
can be used.
Note: Virtual circuits 0-31 on each VPI are reserved for signaling.
Permanent Virtual Circuits
Permanent virtual circuits (PVCs) are created statically. PVCs are configured
in /etc/gratm.conf. The GRF supports Inverse ATM ARP (InATMARP) to
determine the IP address of the other end of the VPI/VCI. If the other device
does not support InATMARP, an ARP entry for the IP and VPI/VCI of the other
device must be made in /etc/grarp.conf.
Note: VPI/VCI pairs must be unique per physical port, and you cannot have
two or more circuits with the same VPI/VCI in the same logical interface.
Switched Virtual Circuits
Switched virtual circuits (SVCs) are created or destroyed dynamically using
standard signaling protocols. These protocols allow ATM devices to create or
destroy connections in response to traffic demands. The VPI/VCI for a given
SVC is determined at the time of the connection setup, and thus requires no
manual configuration in /etc/gratm.conf. However, it is necessary to specify
which of the UNI signaling standards (UNI3.0 or UNI3.1) you wish to use, and
to assign an ARP server. Both sides of the ATM link must use the same
version of the signaling protocol. If you do not wish to use SVCs, set the
signaling for that interface to NONE.
UNI signaling uses ATM Format NSAP addresses, not IP addresses, and
requires the use of an ARP server. The ARP server maps an IP address to an
NSAP address so that ATM signaling can create or use the appropriate SVCs
for traffic destined for the given IP address. The ARP server’s NSAP address
must be configured in the Service section of /etc/gratm.conf.
PVCs and SVCs can be used simultaneously on the same physical interface
(port). PVCs and SVCs can also coexist on the same logical interface.
Verifying an ATM Configuration
maint commands enable you to verify an ATM configuration. They are
described in Section 4.2.7, “Some maint Commands for the ATM OC-3c
Media Card” on page 116; some examples are provided there.