number is eight hex digits long; the leading 0s are not shown. For the network wildcard mask,
all digits are shown in the book, but the leading zeroes are omitted in an actual router
configuration. The mask 0000000F means that the first seven hex digits must match 0000100,
which are the first seven hex digits of the network number in this case, with leading 0s shown.
The last hex digit can be any value. Therefore, networks 1000, 1001, and 14 others are matched.
mask implies that all bits are checked except the one low-order bit. (Feel free to convert hex
1000 and 1001 to binary to see that only the last bit is different in the two numbers.)
do not. This process is fundamental to the job function of a typical CCNA. The SAP process is
very similar to routing updates with a distance vector routing protocol. In fact, SAP uses a split
horizon concept as well. The following sequence outlines a day in the life of a SAP packet:
attached network, based on the expiration of its SAP timer.
its SAP information (up to seven services per packet, by default).
network.
routers and servers receive all the SAP packets.
the SAP packets and update their SAP tables as necessary.
synchronized with the other servers and routers. When the timer
expires, each server and router performs Steps 1 through 3, and
their neighboring servers and routers react and perform Steps 4
through 6.
effectively the same process used by distance vector routing protocols. So, packet filters filter
packets going through a router. Therefore, the IOS uses distribute lists (instead of packet filters)
to filter routing information. Likewise, IOS uses SAP filters to filter SAP information.