Information Technology Reference
In-Depth Information
Methods for Using SRBs (Continued)
Table 4-18
Bridge Type
Function
Remote source route
bridging (RSRB)
Permits the bridging of token rings located on separate routers across non-
Token Ring media. The virtual ring spans the peer routers.
Data-link switching
(DLSw)
DLSw serves as a replacement of SRB and serves SNA data-link connections
(DLC) and NetBIOS traffic. Supports RIF terminations.
RIF
RIF contains a 2-byte RIF header and one or more route descriptors. Each route descriptor
contains a 12-bit ring number and a 4-bit bridge number. The values for the Type field contained
in the header indicate the following:
•
00
—Nonbroadcast (specific route): Indicates that this is a regular frame that should be
routed to the destination following the information in the route descriptors.
•
10
—All-routes broadcast: Indicates that this is an all-rings explorer packet that should
take all possible routes to the destination.
•
11
—Single-route: Indicates that this is a limited broadcast that should take one path to the
destination.
VLAN Trunking
•
ISL—Cisco's proprietary method of trunk encapsulation for carrying VLANs over FE and
GE. You use the VLAN header and trailer outside the frame (external tag).
•
IEEE 802.1q—IEEE standard for trunk encapsulation for carrying VLANs over FE and
GE. Uses internal 4-byte tag that is placed before the Type/Length field of frames.
•
VTP—Cisco's method of distributing VLAN information between Catalyst switches.
•
VLAN pruning—Limits the flooding of broadcasts to switches that do not require them.
FEC
FEC provides a method to increase the bandwidth between two systems by bundling FE links.
FEC also provides load sharing and redundancy capabilities.
CDP
CDP is a Cisco proprietary protocol that you use to obtain hardware platforms and addresses of
neighboring Cisco devices. CDP is media and protocol independent.
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