Now that we have discussed the basis for what goes into a network configuration table, let’s go
through a couple of examples. We will first create the template for what we are looking for, and
then step through the gathering of the necessary information. For these examples, we will first
create a separate network configuration table for routers and one for switches. The network
itself in this example is a small one, containing fewer than 15 routers and 20 switches.
Based on this information, we have decided to include the following list of items in our router
network configuration table:
Device Name
Model #
Location
Flash
DRAM
IOS Version
Interface Name
MAC Address
Subnet
Subnet Mask
IP Address
Routing Protocol
The start of the router network configuration table is shown in Figure 34.1. As you can see
in the figure, part of the information has already been entered for our example. This information
was gathered through a series of
show
commands run on each router. Specifically, the commands
used were
show version
show ip interface brief
show interface
show ip protocols
show ip interface
Though the information in the first two columns of the sample network configuration table
can be obtained through some
show
commands (assuming the
location
or
snmp location
options are set in the router), in our example, as well as in most real-world scenarios, they are
already known by the network administrator doing the work. The next three columns in our
example—Flash, DRAM, and IOS—are all obtained by using the
show version
command:
salmon>
show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-JS-M), Version 12.0(12), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Tue 11-Jul-00 10:09 by htseng
Image text-base: 0x80008088, data-base: 0x80B1468C
ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)
salmon uptime is 3 days, 20 hours, 48 minutes
System restarted power on
System image file is "flash:c2600-js-mz.120-12.bin"
cisco 2610 (MPC860) processor (revision 0x203) with 39936K/9216K bytes
➥
of memory.
Processor board ID JAD04430NYN (832809334)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software (copyright 1990 by Meridian Technology Corp).
TN3270 Emulation software.
Basic Rate ISDN software, Version 1.1.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read/Write)
Configuration register is 0x2102
The flash information is shown at the bottom of the
show version
output, the DRAM is in
the middle, and the IOS is at the top. One item to note is that because the 2610 is a shared memory
router, the DRAM information here is divided into two categories, separated by a slash
character. The first number represents the local memory on the router, and the number on the
right-hand side of the slash represents the I/O memory on the router. The local memory is used
for items such as holding the running IOS, whereas the I/O memory is used for buffers and similar
input and output functions.
To obtain the interfaces that are active on the router, as well as the IP addresses that are
assigned to these interfaces, the
show ip interface brief
command is used:
salmon#
show ip interface brief
Interface IP-Address OK? Method Status Protocol
Ethernet0/0 10.254.254.1 YES NVRAM up up
Serial0/0 10.10.10.1 YES NVRAM up up
Serial0/1 unassigned YES unset administratively down down
Once you have determined which interfaces are used on the router, you can execute the
show
interface
command to get the MAC addresses of the interfaces and the subnet information:
salmon#
show interface e0/0
Ethernet0/0 is up, line protocol is up
Hardware is AmdP2, address is 0004.4d65.b9c0 (bia 0004.4d65.b9c0)
Internet address is 10.254.254.1/24
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255
Encapsulation ARPA, loopback not set, keepalive set (10 sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
27067 packets input, 3624228 bytes, 0 no buffer
Received 27067 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
39804 packets output, 3815083 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
In looking at the output of the
show interface
command, notice that following the MAC
address is the output
(bia 0004.4d65.b9c0)
. The
bia
stands for burned-in address and is the
MAC address that was assigned by Cisco to the interface. The BIA is usually, but not always,
the MAC address that is used on the interface. Specifically, by using the interface-level
macaddress
command, a network administrator can set the MAC address used to any value considered
appropriate.
The final command we’ll examine that is used to populate the network configuration table
is show ip protocols:
salmon#show ip protocols
Routing Protocol is "eigrp 200"
Outgoing update filter list for all interfaces is
Incoming update filter list for all interfaces is
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
EIGRP maximum hopcount 100
EIGRP maximum metric variance 1
Redistributing: eigrp 200
Automatic network summarization is in effect
Routing for Networks:
10.0.0.0
Routing Information Sources:
Gateway Distance Last Update
Distance: internal 90 external 170
The preceding command tells you the routing protocol that is active on the router, as well as
the networks this routing protocol is used for.
One command that was not demonstrated in our example is often used in creation of network
configuration tables: the show ip interface command. In addition to the standard IP
address information, this command provides a wealth of other information such as whether or
not access lists are applied to the interface, the switching methodology of the interface, and
whether or not there is a helper address assigned. Here is a sample output of the show ip
interface command:
salmon#show ip interface e0/0
Ethernet0/0 is up, line protocol is up
Internet address is 10.254.254.1/24
Broadcast address is 255.255.255.255
Address determined by non-volatile memory
MTU is 1500 bytes
Helper address is not set
Directed broadcast forwarding is disabled
Multicast reserved groups joined: 224.0.0.10
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Security level is default
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
IP fast switching is enabled
IP fast switching on the same interface is disabled
IP Flow switching is disabled
IP Fast switching turbo vector
IP multicast fast switching is enabled
IP multicast distributed fast switching is disabled
IP route-cache flags are Fast
Router Discovery is disabled
IP output packet accounting is disabled
IP access violation accounting is disabled
TCP/IP header compression is disabled
RTP/IP header compression is disabled
Probe proxy name replies are disabled
Policy routing is disabled
Network address translation is disabled
Web Cache Redirect is disabled
BGP Policy Mapping is disabled