Introduction
Cisco IOS Routers and Switches
Identifying the Effectiveness of Infrastructure Access Control Lists
Transit Access Control Lists
Identifying the Effectiveness of Transit Access Control Lists
Identifying the Effectiveness of Access List Logging
Spoofing Protections
Unicast Reverse Path Forwarding
IP Source Guard
Identifying the Effectiveness of Spoofing Protection Using Unicast Reverse Path Forwarding
IPv4 and IPv6 Identification
Cisco IOS NetFlow and Cisco IOS Flexible NetFlow
Identifying the Effectiveness of IPv4 Traffic Flow Identification Using Cisco IOS NetFlow
Identifying the Effectiveness of IPv6 Traffic Flow Identification Using Cisco IOS NetFlow
Identifying the Effectiveness of IPv4 Traffic Flow Identification Using Cisco IOS Flexible NetFlow
Identifying the Effectiveness of IPv6 Traffic Flow Identification Using Cisco IOS Flexible NetFlow
Cisco IOS Software Zone-Based Firewall
Identifying the Effectiveness of Cisco IOS Software Zone-Based Firewall on Cisco IOS Routers
Conclusion
Additional Information
Risk Management
Resources
Cisco IOS Software can provide effective means of exploit prevention using the following methods:
This document provides identification techniques that administrators can deploy on Cisco network devices to identify whether the prevention methods are having the desired effect. Readers of this document will understand that the specific commands used in this document will differ from production devices depending on the traffic being blocked.
Caution: The effectiveness of any mitigation technique depends on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. As with any configuration change, evaluate the impact of this configuration prior to applying the change.
Specific information about identification is available for these Cisco IOS devices:
After the administrator applies an iACL to an interface, the show ip access-lists and show ipv6 access-list commands will identify the number of IP version 4 (IPv4) and IP version 6 (IPv6) packets that have been filtered on interfaces on which the iACL is applied. Administrators should investigate filtered packets to determine whether they are attempts to exploit security vulnerabilities. Example output for show ip access-lists Infrastructure-ACL-Policy and show ipv6 access-list IPv6-Infrastructure-ACL-Policy follows:
router#show ip access-lists Infrastructure-ACL-Policy
Extended IP access list Infrastructure-ACL-Policy
10 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5060 (60 matches)
20 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5061 (41 matches)
30 permit udp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5060 (188 matches)
40 permit udp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5061 (51 matches)
50 deny tcp any 192.168.60.0 0.0.0.255 eq 5060 (9 matches)
60 deny tcp any 192.168.60.0 0.0.0.255 eq 5061 (18 matches)
70 deny udp any 192.168.60.0 0.0.0.255 eq 5060 (34 matches)
80 deny udp any 192.168.60.0 0.0.0.255 eq 5061 (72 matches)
90 deny ip any 192.168.60.0 0.0.0.255 (17 matches)
router#
In the preceding example, access list Infrastructure-ACL-Policy has dropped the following packets received from an untrusted host or network:
router#show ipv6 access-list IPv6-Infrastructure-ACL-Policy
IPv6 access list IPv6-Infrastructure-ACL-Policy
permit tcp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5060 (71 matches) sequence 10
permit tcp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5061 (85 matches) sequence 20
permit udp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5060 (512 matches) sequence 30
permit udp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5061 (171 matches) sequence 40
deny tcp any 2001:DB8:1:60::/64 eq 5060 (58 matches) sequence 50
deny tcp any 2001:DB8:1:60::/64 eq 5061 (81 matches) sequence 60
deny udp any 2001:DB8:1:60::/64 eq 5060 (216 matches) sequence 70
deny udp any 2001:DB8:1:60::/64 eq 5061 (114 matches) sequence 80
permit icmp any any nd-ns (80 matches) sequence 90
permit icmp any any nd-na (80 matches) sequence 100
deny ipv6 any 2001:DB8:1:60::/64 (5 matches) sequence 110In the preceding example, access list IPv6-Infrastructure-ACL-Policy has dropped the following packets received from an untrusted host or network:
For additional information about investigating incidents using ACE counters and syslog events, see the Identifying Incidents Using Firewall and IOS Router Syslog Events Cisco Security Intelligence Operations white paper.
Administrators can use Embedded Event Manager to provide instrumentation when specific conditions are met, such as ACE counter hits. The Cisco Security Intelligence Operations white paper Embedded Event Manager in a Security Context provides additional details about how to use this feature.
To protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy transit access control lists (tACLs) to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against security vulnerabilities when the attack originates from a trusted source address.
Identifying the Effectiveness of Transit Access Control Lists
After the administrator applies the tACL to an interface, show ip access-lists and show ipv6 access-list commands will identify the number of IPv4 and IPv6 packets that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit security vulnerabilities. Example output for show ip access-lists 150 andshow ipv6 access-list IPv6-Transit-ACL-Policy follows:
router#show ip access-lists 150
Extended IP access list 150
10 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 139
20 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 445
30 deny tcp any 192.168.60.0 0.0.0.255 eq 139 (12 matches)
40 deny tcp any 192.168.60.0 0.0.0.255 eq 445 (26 matches)
50 deny ip any any
router#In the preceding example, access list 150 has dropped the following packets received from an untrusted host or network:
router#show ipv6 access-list IPv6-Transit-ACL-Policy
IPv6 access list IPv6-Transit-ACL-Policy
permit tcp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5060 (55 matches) sequence 10
permit tcp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5061 (38 matches) sequence 20
permit udp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5060 (210 matches) sequence 30
permit udp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5061 (59 matches) sequence 40
deny tcp any 2001:DB8:1:60::/64 eq 5060 (30 matches) sequence 50
deny tcp any 2001:DB8:1:60::/64 eq 5061 (41 matches) sequence 60
deny udp any 2001:DB8:1:60::/64 eq 5060 (310 matches) sequence 70
deny udp any 2001:DB8:1:60::/64 eq 5061 (131 matches) sequence 80
permit icmp any any nd-ns (41 matches) sequence 90
permit icmp any any nd-na (41 matches) sequence 100
deny ipv6 any any (21 matches) sequence 110In the preceding example, access list IPv6-Transit-ACL-Policy has dropped the following packets received from an untrusted host or network:
For additional information about investigating incidents using ACE counters and syslog events, see the Identifying Incidents Using Firewall and IOS Router Syslog Events Cisco Security Intelligence Operations white paper.
Administrators can use Embedded Event Manager to provide instrumentation when specific conditions are met, such as ACE counter hits. The Cisco Security Intelligence Operations white paper Embedded Event Manager in a Security Context provides additional details about how to use this feature.
The log and log-input access control list (ACL) option will cause packets that match specific ACEs to be logged. The log-input option enables logging of the ingress interface in addition to the packet source and destination IP addresses and ports.
Caution: Access control list logging can be very CPU intensive and must be used with extreme caution. Factors that drive the CPU impact of ACL logging are log generation, log transmission, and process switching to forward packets that match log-enabled ACEs.
For Cisco IOS Software, the ip access-list logging interval interval-in-ms command can limit the effects of process switching induced by IPv4 ACL logging. The logging rate-limit rate-per-second [except loglevel] command limits the impact of log generation and transmission.
The CPU impact from ACL logging can be addressed in hardware on the Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers with Supervisor Engine 720 or Supervisor Engine 32 using optimized ACL logging.
For additional information about the configuration and use of ACL logging, see the Understanding Access Control List Logging Cisco Security Intelligence Operations white paper.
Unicast Reverse Path Forwarding
Security vulnerabilities can be exploited by spoofed IP packets. Administrators can deploy and configure Unicast Reverse Path Forwarding (uRPF) as a protection mechanism against spoofing.
uRPF is configured at the interface level and can detect and drop packets that lack a verifiable source IP address. Administrators should not rely on uRPF to provide complete spoofing protection because spoofed packets may enter the network through a uRPF-enabled interface if an appropriate return route to the source IP address exists. Administrators are advised to take care to ensure that the appropriate uRPF mode (loose or strict) is configured during the deployment of this feature because it can drop legitimate traffic that is transiting the network. In an enterprise environment, uRPF may be enabled at the Internet edge and the internal access layer on the user-supporting Layer 3 interfaces.
For additional information about the configuration and use of uRPF, see the Understanding Unicast Reverse Path Forwarding Cisco Security Intelligence Operations white paper.
IP Source Guard
IP source guard (IPSG) is a security feature that restricts IP traffic on nonrouted, Layer 2 interfaces by filtering packets based on the DHCP snooping binding database and manually configured IP source bindings. Administrators can use IPSG to prevent attacks from an attacker who attempts to spoof packets by forging the source IP address and/or the MAC address. When properly deployed and configured, IPSG coupled with strict mode uRPF provides the most effective means of spoofing protection for security vulnerabilities.
Additional information about the deployment and configuration of IPSG is in Configuring DHCP Features and IP Source Guard.
Identifying the Effectiveness of Spoofing Protection Using Unicast Reverse Path Forwarding
With uRPF properly deployed and configured throughout the network infrastructure, administrators can use the show cef interface type slot/port internal, show ip interface, show cef drop, show ip cef switching statistics feature, and show ip traffic commands to identify the number of packets that uRPF has dropped.
Note: Beginning with Cisco IOS Software Release 12.4(20)T, the command show ip cef switching has been replaced by show ip cef switching statistics feature.
Note: The show command | begin regex and show command | include regex command modifiers are used in the following examples to minimize the amount of output that administrators will need to parse to view the desired information. Additional information about command modifiers is in the show command sections of the Cisco IOS Configuration Fundamentals Command Reference.
router#show cef interface GigabitEthernet 0/0 internal | include drop ip verify: via=rx (allow default), acl=0, drop=18, sdrop=0 IPv6 unicast RPF: via=rx acl=None, drop=10, sdrop=0 (if IPv6 applies) router#
Note: show cef interface type slot/port internal is a hidden command that must be fully entered at the command-line interface. Command completion is not available for it.
router#show cef drop CEF Drop Statistics Slot Encap_fail Unresolved Unsupported No_route No_adj ChkSum_Err RP 27 0 0 18 0 0 router# router#show ip interface GigabitEthernet 0/0 | begin verify IP verify source reachable-via RX, allow default, allow self-ping 18 verification drops 0 suppressed verification drops router# router#show ipv6 interface GigabitEthernet 0/0 | section IPv6 verify IPv6 verify source reachable-via rx 0 verification drop(s) (process), 10 (CEF) 0 suppressed verification drop(s) (process), 0 (CEF) -- CLI Output Truncated -- router# router#show ip cef switching statistics feature IPv4 CEF input features:
Path Feature Drop Consume Punt Punt2Host Gave route
RP PAS uRPF 18 0 0 0 0 Total 18 0 0 0 0 -- CLI Output Truncated -- router# router#show ipv6 cef switching statistics feature IPv6 CEF input features: Feature Drop Consume Punt Punt2Host Gave route RP LES Verify Unicast R 10 0 0 0 0 Total 10 0 0 0 0 -- CLI Output Truncated -- router# router#show ip traffic | include RPF 18 no route, 18 unicast RPF, 0 forced drop router# router#show ipv6 traffic | include RPF 10 RPF drops, 0 RPF suppressed, 0 forced drop router#
In the preceding show cef interface GigabitEthernet 0/0 internal, show cef drop, show ip interface GigabitEthernet 0/0 and show ipv6 interface GigabitEthernet 0/0 , show ip cef switching statistics feature and show ipv6 cef switching statistics feature, and show ip traffic and show ipv6 traffic examples, uRPF has dropped the following packets received globally on all interfaces that have uRPF configured. The packets were dropped because of the inability to verify the source address of the IP packets within the forwarding information base of Cisco Express Forwarding.
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and switches to aid in the identification of IPv4 traffic flows that may be attempts to exploit security vulnerabilities. Administrators are advised to investigate flows to determine whether they are attempts to exploit the vulnerabilities or whether they are legitimate traffic flows.
router#show ip cache flow
IP packet size distribution (90784136 total packets):
1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .698 .011 .001 .004 .005 .000 .004 .000 .000 .003 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .001 .256 .000 .010 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 4456704 bytes
1885 active, 63651 inactive, 59960004 added
129803821 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 402056 bytes
0 active, 16384 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol Total Flows Packets Bytes Packets Active(Sec) Idle(Sec)
-------- Flows /Sec /Flow /Pkt /Sec /Flow /Flow
TCP-Telnet 11393421 2.8 1 48 3.1 0.0 1.4
TCP-FTP 236 0.0 12 66 0.0 1.8 4.8
TCP-FTPD 21 0.0 13726 1294 0.0 18.4 4.1
TCP-WWW 22282 0.0 21 1020 0.1 4.1 7.3
TCP-X 719 0.0 1 40 0.0 0.0 1.3
TCP-BGP 1 0.0 1 40 0.0 0.0 15.0
TCP-Frag 70399 0.0 1 688 0.0 0.0 22.7
TCP-other 47861004 11.8 1 211 18.9 0.0 1.3
UDP-DNS 582 0.0 4 73 0.0 3.4 15.4
UDP-NTP 287252 0.0 1 76 0.0 0.0 15.5
UDP-other 310347 0.0 2 230 0.1 0.6 15.9
ICMP 11674 0.0 3 61 0.0 19.8 15.5
IPv6INIP 15 0.0 1 1132 0.0 0.0 15.4
GRE 4 0.0 1 48 0.0 0.0 15.3
Total: 59957957 14.8 1 196 22.5 0.0 1.5
SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts
Gi0/0 192.168.10.201 Gi0/1 192.168.60.102 11 0984 00A1 1
Gi0/0 192.168.11.54 Gi0/1 192.168.60.158 11 0911 00A1 3
Gi0/1 192.168.150.60 Gi0/0 10.89.16.226 06 0016 12CA 1
Gi0/0 192.168.13.97 Gi0/1 192.168.60.28 11 0B3E 00A1 5
Gi0/0 192.168.10.17 Gi0/1 192.168.60.97 11 0B89 00A1 1
Gi0/0 10.88.226.1 Gi0/1 192.168.202.22 11 007B 007B 1
Gi0/0 192.168.12.185 Gi0/1 192.168.60.239 11 0BD7 00A1 1
Gi0/0 10.89.16.226 Gi0/1 192.168.150.60 06 12CA 0016 1
router#In the preceding example, there are multiple flows for SNMP on UDP port 161 (hex value 00A1).
If this traffic is sourced from and sent to addresses within the 192.168.60.0/24 address block, which is used by affected devices, the packets in these flows may be spoofed and may indicate an attempt to exploit security vulnerabilities. Administrators are advised to compare these flows to baseline utilization for SNMP on UDP port 161 and also investigate the flows to determine whether they are sourced from untrusted hosts or networks.
If administrators are interested only in a specific type of TCP flow, the following example shows only the SSH packets on TCP port 22 (hex value 0016). Use the show ip cache flow | include SrcIf|_06_.*0016 command to display the related Cisco NetFlow records:
router#show ip cache flow | include SrcIf|_06_.*0016 SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Gi0/0 192.168.12.110 Gi0/1 192.168.60.163 06 092A 0016 6 Gi0/0 192.168.11.230 Gi0/1 192.168.60.20 06 0C09 0016 1 Gi0/0 192.168.11.131 Gi0/1 192.168.60.245 06 0B66 0016 18 Gi0/0 192.168.13.7 Gi0/1 192.168.60.162 06 0914 0016 1 Gi0/0 192.168.41.86 Gi0/1 192.168.60.27 06 0B7B 0016 2 router#
As shown in the following example, to view only the SNMP packets on UDP port 161 (hex value 00A1), use show ip cache flow | include SrcIf|_11_.*00A1
Note: For multiple destination ports, use the following format: show ip cache flow | include SrcIf|_PrHex_.*(DstP1Hex|DstP2Hex|DstP3Hex)_ command to display the related Cisco NetFlow records.
router#show ip cache flow | include SrcIf|_11_.*00A1 SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Gi0/0 192.168.12.110 Gi0/1 192.168.60.163 11 092A 00A1 6 Gi0/0 192.168.11.230 Gi0/1 192.168.60.20 11 0C09 00A1 1 Gi0/0 192.168.11.131 Gi0/1 192.168.60.245 11 0B66 00A1 18 Gi0/0 192.168.13.7 Gi0/1 192.168.60.162 11 0914 00A1 1 Gi0/0 192.168.41.86 Gi0/1 192.168.60.27 11 0B7B 00A1 2 router#
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and switches to aid in the identification of IPv6 traffic flows that may be attempts to exploit security vulnerabilities. Administrators are advised to investigate flows to determine whether they are attempts to exploit vulnerabilities or whether they are legitimate traffic flows.
The following output is from a Cisco IOS device running the Cisco IOS Software 12.4 mainline train. The command syntax will vary for different Cisco IOS Software trains.
router#show ipv6 flow cache
IP packet size distribution (50078919 total packets):
1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .990 .001 .008 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 475168 bytes
8 active, 4088 inactive, 6160 added
1092984 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 33928 bytes
16 active, 1008 inactive, 12320 added, 6160 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
SrcAddress InpIf DstAddress OutIf Prot SrcPrt DstPrt Packets
2001:DB...06::201 Gi0/0 2001:DB...28::20 Local 0x11 0x16C4 0x13C4 1464
2001:DB...6A:5BA6 Gi0/0 2001:DB...28::21 Gi0/1 0x3A 0x0000 0x8000 1191
2001:DB...6A:5BA6 Gi0/0 2001:DB...134::3 Gi0/1 0x3A 0x0000 0x8000 1191
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::4 Gi0/1 0x3A 0x0000 0x8000 1192
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::2 Gi0/1 0x06 0x160A 0x13C4 1597
2001:DB...06::201 Gi0/0 2001:DB...128::3 Gi0/1 0x11 0x1610 0x13C5 1001
2001:DB...06::201 Gi0/0 2001:DB...128::4 Gi0/1 0x11 0x1634 0x13C4 1292
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::3 Gi0/1 0x3A 0x0000 0x8000 1155
2001:DB...6A:5BA6 Gi0/0 2001:DB...146::3 Gi0/1 0x3A 0x0000 0x8000 1092
2001:DB...6A:5BA6 Gi0/0 2001:DB...144::4 Gi0/1 0x3A 0x0000 0x8000 1193 To permit display of the full 128-bit IPv6 address, use the terminal width 132 exec mode command.
In the preceding example, there are multiple IPv6 flows for SIP on TCP port 5060 (hex value 13C4) and UDP ports 5060 (hex value 13C4) and 5061 (hex value 13C5).
If the packets on the UDP ports are sourced from and sent to addresses within the 2001:DB8:1:60::/64 address block that is used by affected devices, the packets in the UDP flows may be spoofed and could indicate an attempt to exploit security vulnerabilities. Administrators are advised to compare these flows to baseline utilization (such as SIP in the above example) and also investigate the flows to determine whether they are sourced from untrusted hosts or networks.
As shown in the following example, to view only the SIP packets on TCP port 5060 (hex value 13C4), use show ipv6 flow cache | include SrcIf|_06_.*13C4
Note: For multiple destination ports, use the following format: show ipv6 flow cache | include SrcIf|_PrHex_.*(DstP1Hex|DstP2Hex|DstP3Hex)_ command to display the related Cisco NetFlow records:
router#show ipv6 flow cache | include SrcIf|_06_.*(13C4)_ SrcAddress InpIf DstAddress OutIf Prot SrcPrt DstPrt Packets 2001:DB...6A:5BA6 Gi0/0 2001:DB...128::2 Gi0/1 0x06 0x160A 0x13C4 1597 router#
As shown in the following example, to view only the SIP packets on UDP port 5060 (hex value 13C4) and UDP port 5061 (hex value 13C5), use show ipv6 flow cache | include SrcIf|_PrHex_.*(DstP1Hex|DstP2Hex)_
router#show ipv6 flow cache | include SrcIf|_11_.*(13C4|13C5)_ SrcAddress InpIf DstAddress OutIf Prot SrcPrt DstPrt Packets 2001:DB...06::201 Gi0/0 2001:DB...28::20 Local 0x11 0x16C4 0x13C4 1464 2001:DB...06::201 Gi0/0 2001:DB...128::3 Gi0/1 0x11 0x1610 0x13C5 1001 2001:DB...06::201 Gi0/0 2001:DB...128::4 Gi0/1 0x11 0x1634 0x13C4 1292 router#
Introduced in Cisco IOS Software Releases 12.2(31)SB2 and 12.4(9)T, Cisco IOS Flexible NetFlow improves original Cisco NetFlow by adding the capability to customize the traffic analysis parameters for the administrator's specific requirements. Original Cisco NetFlow uses a fixed seven tuples of IP information to identify a flow, whereas Cisco IOS Flexible NetFlow allows the flow to be user defined. It facilitates the creation of more complex configurations for traffic analysis and data export by using reusable configuration components.
The following example output is from a Cisco IOS device that is running a version of Cisco IOS Software in the 15.1T train. Although the syntax will be almost identical for the 12.4T and 15.0 trains, it may vary slightly depending on the actual Cisco IOS release being used. In the following configuration, Cisco IOS Flexible NetFlow will collect information on interface GigabitEthernet0/0 for incoming IPv4 flows based on source IPv4 address, as defined by the match ipv4 source address key field statement. Cisco IOS Flexible NetFlow will also include nonkey field information about source and destination IPv4 addresses, protocol, ports (if present), ingress and egress interfaces, and packets per flow.
! !-- Configure key and nonkey fields !-- in the user-defined flow record ! flow record FLOW-RECORD-ipv4 match ipv4 source address collect ipv4 protocol collect ipv4 destination address collect transport source-port collect transport destination-port collect interface input collect interface output collect counter packets ! !-- Configure the flow monitor to !-- reference the user-defined flow !-- record ! flow monitor FLOW-MONITOR-ipv4 record FLOW-RECORD-ipv4 ! !-- Apply the flow monitor to the interface !-- in the ingress direction ! interface GigabitEthernet0/0 ip flow monitor FLOW-MONITOR-ipv4 input
The Cisco IOS Flexible NetFlow flow output is as follows:
router#show flow monitor FLOW-MONITOR-ipv4 cache format table
Cache type: Normal
Cache size: 4096
Current entries: 6
High Watermark: 1
Flows added: 9181
Flows aged: 9175
- Active timeout ( 1800 secs) 9000
- Inactive timeout ( 15 secs) 175
- Event aged 0
- Watermark aged 0
- Emergency aged 0
IPV4 SRC ADDR ipv4 dst addr trns src port trns dst port intf input intf output pkts ip prot
=============== =============== ============= ============= ========== =========== ====== =======
192.168.10.201 192.168.60.102 1456 80 Gi0/0 Gi0/1 1128 6
192.168.11.54 192.168.60.158 123 123 Gi0/0 Gi0/1 2212 17
192.168.150.60 10.89.16.226 2567 443 Gi0/0 Gi0/1 13 6
192.168.13.97 192.168.60.28 3451 80 Gi0/0 Gi0/1 1 6
192.168.10.17 192.168.60.97 4231 5060 Gi0/0 Gi0/1 146 17
10.88.226.1 192.168.202.22 2678 443 Gi0/0 Gi0/1 10567 6
10.89.16.226 192.168.150.60 3562 80 Gi0/0 Gi0/1 30012 6To view only the packets on TCP port 80, use the show flow monitor FLOW-MONITOR-ipv4 cache format table | include IPV4 DST ADDR |_(80)_.*_6_ command to display the related NetFlow records.
For more information about Cisco IOS Flexible NetFlow, see Flexible Netflow Configuration Guide, Cisco IOS Release 15M&T.
The following example output is from a Cisco IOS device that is running a version of Cisco IOS Software in the 15.1T train. Although the syntax will be almost identical for the 12.4T and 15.0 trains, it may vary slightly depending on the actual Cisco IOS release being used. In the following configuration, Cisco IOS Flexible NetFlow will collect information on interface GigabitEthernet0/0 for incoming IPv6 flows based on the source IPv6 address, as defined by the match ipv6 source address key field statement. Cisco IOS Flexible NetFlow will also include nonkey field information about source and destination IPv6 addresses, protocol, ports (if present), ingress and egress interfaces, and packets per flow.
! !-- Configure key and nonkey fields !-- in the user-defined flow record ! flow record FLOW-RECORD-ipv6 match ipv6 source address collect ipv6 protocol collect ipv6 destination address collect transport source-port collect transport destination-port collect interface input collect interface output collect counter packets ! !-- Configure the flow monitor to !-- reference the user-defined flow !-- record ! flow monitor FLOW-MONITOR-ipv6 record FLOW-RECORD-ipv6 ! !-- Apply the flow monitor to the interface !-- in the ingress direction ! interface GigabitEthernet0/0 ipv6 flow monitor FLOW-MONITOR-ipv6 input
The Cisco IOS Flexible NetFlow flow output is as follows:
router#show flow monitor FLOW-MONITOR-ipv6 cache format table
Cache type: Normal
Cache size: 4096
Current entries: 6
High Watermark: 2
Flows added: 539
Flows aged: 532
- Active timeout ( 1800 secs) 350
- Inactive timeout ( 15 secs) 182
- Event aged 0
- Watermark aged 0
- Emergency aged 0
IPV6 SRC ADDR ipv6 dst addr trns src port trns dst port intf input intf output pkts ip prot
================= ================= ============= ============= ========== =========== ==== =======
2001:DB...06::201 2001:DB...28::20 123 123 Gi0/0 Gi0/0 17 17
2001:DB...06::201 2001:DB...28::20 1265 80 Gi0/0 Gi0/0 1237 6
2001:DB...06::201 2001:DB...28::20 1441 443 Gi0/0 Gi0/0 2346 6
2001:DB...06::201 2001:DB...28::20 1890 80 Gi0/0 Gi0/0 5009 6
2001:DB...06::201 2001:DB...28::20 2856 5060 Gi0/0 Gi0/0 486 17
2001:DB...06::201 2001:DB...28::20 3012 53 Gi0/0 Gi0/0 1016 17
2001:DB...06::201 2001:DB...28::20 2477 53 Gi0/0 Gi0/0 1563 17To permit display of the full 128-bit IPv6 address, use the terminal width 132 exec mode command.
To view only the packets on TCP port 443, use the show flow monitor FLOW-MONITOR-ipv6 cache format table | include IPV6 DST ADDR|_(443)_.*_6_ command to display the related Cisco IOS Flexible NetFlow records.
The Cisco IOS Software Zone-Based Firewall is an advanced stateful firewall method for Cisco IOS routers. It changes the older Context-Based Access Control (CBAC ) to a more flexible zone-based model that employs inter-zone policies for more flexibility and granularity.
The following example shows a configuration for the Zone-Based Firewall. Traffic may be initiated only from the private to public zone for SIP, and all other traffic will be dropped for either direction, inbound or outbound. The example shows 4 dropped packets for the default drop action.
router#show policy-map type inspect zone-pair
Zone-pair: priv-pub
Service-policy inspect : priv-pub-pmap
Class-map: private-sip (match-all)
Match: protocol sip
Inspect
Packet inspection statistics [process switch:fast switch]
udp packets: [8800:70]
Session creations since subsystem startup or last reset 731
Current session counts (estab/half-open/terminating) [0:0:0]
Maxever session counts (estab/half-open/terminating) [0:3:0]
Last session created 00:00:25
Last statistic reset never
Last session creation rate 0
Maxever session creation rate 4
Last half-open session total 0
Class-map: class-default (match-any)
Match: any
Drop (default action)
4 packets, 112 bytesIn summary, network administrators and security engineers can use the vulnerability exploit attempt identification techniques presented in this document to identify vulnerability exploit attempts. These techniques can be leveraged by using the attack vector characteristics of the vulnerability investigated in place of the example attack vectors used in the document. Administrators can then ensure that the exploit attempts do not have any impact on the network.
Organizations are advised to follow their standard risk evaluation and mitigation processes to determine the potential impact of vulnerabilities. Triage refers to sorting projects and prioritizing efforts that are most likely to be successful. Cisco has provided documents that can help organizations develop a risk-based triage capability for their information security teams. Risk Triage for Security Vulnerability Announcements and Risk Triage and Prototyping can help organizations develop repeatable security evaluation and response processes.
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