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Trace 7.1a. IP routing table retrieval (summary)
Sniffer Network Analyzer data 5-Oct at 09:04:44, file NAME.ENC Pg 1
SUMMARY Delta T Destination Source Summary
9 0.0043 Agent Manager sNMP GetNext ipRouteDest..
ipRouteIf Index
(4 items)
10 0.0102 Manager Agent SNMP GetReply ipRouteDest
.. ipRouteIfIndex (4 items)
11 0.0482 Agent Manager SNMP GetNext ipRouteDest
.. ipRouteIfIndex (4 items)
53 0.0662 Agent Manager SNMP GetNext ipRouteDest
.. ipRouteIfIndex (4 items)
54 0.0104 Manager Agent SNMP GetReply
ipRouteDest .. ipRouteIfIndex
(4 items)
55 0.0687 Agent Manager SNMP GetNext ipRouteDest
.. ipRouteIfIndex (4 items)
56 0.0138 Manager Agent SNMP GetReply
ipRouteIfIndex ..
ipRouteMetric1
(4 items)
57 65.7201 HP133ADE HP17B65F ARP C PA=[128.79.3.105] PRO=IP
58 0.0005 HP17B65F HP133ADE ARP R PA=[128.79.3.105]
HA=080009133ADE PRO=IP
59 82.5076 Agent Manager ICMP Echo
60 0.0008 Manager Agent ICMP Echo reply
61 50.1077 Agent Manager SNMP GetNext ifIndex
.. ifPhysAddress (3 items)
62 4.9924 Agent Manager SNMP GetNext ifIndex
.. ifPhysAddress (3 items)
63 5.0003 Agent Manager SNMP GetNext ifIndex
.. ifPhysAddress (3 items)
Trace 7.1b. IP routing table retrieval details (GetNext Requests)
Sniffer Network Analyzer data 5-Oct at 09:04:44, file NAME.ENC
Pg 1
------------------------- Frame 9 -----------------------------
SNMP: ----- Simple Network Management Protocol (Version 1)-----
SNMP:
SNMP: Version = 0
SNMP: Community = public
SNMP: Command = Get next request
SNMP: Request ID = 11386
SNMP: Error status = 0 (No error)
SNMP: Error index = 0
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.1} (ipRouteDest)
SNMP: Value = NULL
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.7} (ipRouteNextHop)
SNMP: Value = NULL
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.8} (ipRouteType)
SNMP: Value = NULL
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.2} (ipRouteIfIndex)
SNMP: Value = NULL
SNMP:
-------------------------- Frame 10 ---------------------------
SNMP: ----- Simple Network Management Protocol (Version 1) ----
SNMP:
SNMP: Version = 0
SNMP: Community = public
SNMP: Command = Get response
SNMP: Request ID = 11386
SNMP: Error status = 0 (No error)
SNMP: Error index = 0
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.1.0.0.0.0}
(ipRouteDest.0.0.0.0)
SNMP: Value = [0.0.0.0]
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.7.0.0.0.0}
(ipRouteNextHop.0.0.0.0)
SNMP: Value = [128.79.3.200]
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.8.0.0.0.0}
(ipRouteType.0.0.0.0)
SNMP: Value = 4 (indirect)
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.2.0.0.0.0}
(ipRouteIfIndex.0.0.0.0)
SNMP: Value = 2
SNMP:
Trace 7.1c. IP routing table retrieval details (End of GetNext)
Sniffer Network Analyzer data 5-Oct at 09:04:44, file NAME.ENC
Pg 1
-------------------------- Frame 55 ---------------------------
SNMP: ----- Simple Network Management Protocol (Version 1)-----
SNMP:
SNMP: Version = 0
SNMP: Community = public
SNMP: Command = Get next request
SNMP: Request ID = 11409
SNMP: Error status = 0 (No error)
SNMP: Error index = 0
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.1.128.79.200.0}
(ipRouteDest.128.79.200.0)
SNMP: Value = NULL
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.7.128.79.200.0}
(ipRouteNextHop.128.79.200.0)
SNMP: Value = NULL
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.8.128.79.200.0}
(ipRouteType.128.79.200.0)
SNMP: Value = NULL
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.2.128.79.200.0}
(ipRouteIfIndex.128.79.200.0)
SNMP: Value = NULL
SNMP:
-------------------------- Frame 56 ---------------------------
SNMP: ----- Simple Network Management Protocol (Version 1) ----
SNMP:
SNMP: Version = 0
SNMP: Community = public
SNMP: Command = Get response
SNMP: Request ID = 11409
SNMP: Error status = 0 (No error)
SNMP: Error index = 0
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.2.0.0.0.0} (ipRouteIfIndex.0.0.0.0)
SNMP: Value = 2
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.8.0.0.0.0} (ipRouteType.0.0.0.0)
SNMP: Value = 4 (indirect)
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.9.0.0.0.0} (ipRouteProto.0.0.0.0)
SNMP: Value = 2 (local)
SNMP:
SNMP: Object = {1.3.6.1.2.1.4.21.1.3.0.0.0.0} (ipRouteMetric1.0.0.0.0)
SNMP: Value = 1
SNMP:
7.2 Verifying Access Control with the Community Name and IP Address
Many network devices, such as routers, allow the network administrator to configure multiple SNMP community names for remote access. In addition, the network device can have a filter that specifies the IP address of the remote manager. Thus, the combination of the community name and the IP address acts as a two–level method of remote access security.
In this example, a router was configured with two SNMP communities (see Figure 7-2). The first uses community name = abcsnmp and allows access with IP address [XXX.YYY.ZZZ.145]. The second uses community name = xyzsnmp and allows access with IP address [XXX.YYY.ZZZ.146]. Let's see how the router reacts to an invalid request.
)
Figure 7-2 Agent access from multiple communities
In Frame 64 of Trace 7.2a, Manager 145 issues a GetRequest for the value of the sysDescr object. As you can see in Frame 64 of Trace 7.2b, that GetRequest includes the community name = abcsnmp. Since a match exists between the community name and the IP address, the router issues a GetResponse (Frame 65) containing the system description
Value = /usr3/wf/wf.rel/v5.75/wf.pj/proto.ss/ace_test.p/
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