Well this is the most CIsco IOS basics commands and perhaps useful for some of you, who are beginning to experience with this products.
The following Cisco IOS commands explained in the video below are used for file management:
dir, cd, copy, delete, rm, show flash, erase, format, more, verify, mkdir, fsck
The tutorial is work of Bill Detwiler at TechRepublic.com.
Official document on Cisco Security Advisory website
Cisco IOS XR Software contains multiple vulnerabilities in the Border Gateway Protocol (BGP) feature. These vulnerabilities include:
Cisco IOS XR Software will reset a BGP peering session when receiving a specific invalid BGP update.
The vulnerability manifests when a BGP peer announces a prefix with a specific invalid attribute. On receipt of this prefix, the Cisco IOS XR device will restart the peering session by sending a notification. The peering session will flap until the sender stops sending the invalid/corrupt update. This vulnerability was disclosed in revision 1.0 of this advisory.
Cisco IOS XR BGP process will crash when sending a long length BGP update message.
When Cisco IOS XR sends a long length BGP update message, the BGP process may crash. The number of AS numbers required to exceed the total/maximum length of update message and cause the crash are well above normal limits seen within production environments.
Cisco IOS XR BGP process will crash when constructing a BGP update with a large number of AS prepends.
If the Cisco IOS XR BGP process is configured to prepend a very large number of Autonomous System (AS) Numbers to the AS path, the BGP process will crash. The number of AS numbers required to be prepended and cause the crash are well above normal limits seen within production environments.All three vulnerabilities are different vulnerabilities from what was disclosed in the Cisco Security Advisory “Cisco IOS Software Border Gateway Protocol 4-Byte Autonomous System Number Vulnerabilities” on the 2009 July 29 1600 UTC.
The “Cisco IOS XR Software will reset a BGP peering session when receiving a specific invalid BGP update” vulnerability affects all Cisco IOS XR Software devices after and including software release 3.4.0 configured with BGP routing.
The other two vulnerabilities affect all Cisco IOS XR Software devices configured with BGP routing.
Cisco IOS XR Software will reset a BGP peering session when receiving a specific invalid BGP update.
There are no workarounds on the affected device itself. Co-ordination is required with the peering neighbor support staff to filter the invalid update on their outbound path. The following procedure explains how to help mitigate this vulnerability:
Using the peer IP address in the log message that was generated when the Cisco IOS XR Software device received the invalid update; capture the notification message hex dump from the CLI command show bgp neighbor and contact the Cisco TAC, who can assist with a decode. Details on how to contact Cisco TAC are contained within the “Obtaining Fixed Software” section of this advisory.
For illustrative purposes, the following example shows a log message generated by an affected device when it receives an invalid/corrupt update message:
RP/0/RP0/CPU0:Aug 17 13:47:05.896 GMT: bgp[122]: %ROUTING-BGP-5-ADJCHANGE : neighbor 192.168.0.1 Down - BGP Notification sent: invalid or corrupt AS path
These details can be captured and provided to Cisco TAC to decode the update message. show bgp neighbors [ip address of neighbor from above log message]:
RP/0/RP0/CPU0:CRS#show bgp neighbors 192.168.0.1 <capture output and provide to Cisco TAC>
Working with Cisco TAC, the decode of the above will display the AS path in a manner illustrated below.
ATTRIBUTE NAME: AS_PATH AS_PATH: Type 2 is AS_SEQUENCE AS_PATH: Segment Length is 4 (0x04) segments long AS_PATH: 65533 65532 65531 65531
Working cooperatively with your peering partner, request that they filter outbound prefix advertisements from the identified source AS (in this example 65531) for your peering session. The filters configuration methods will vary depending on the routing device operating system used. For Cisco IOS XR Software the filters will be applied using Routing Policy Language (RPL) policies or with Cisco IOS Software via applying route-maps that deny advertisements matching that AS in their AS-PATH. Once these policies are applied, the peering session will be re-established.
For further information on Cisco IOS XR RPL consult the document “Implementing Routing Policy on Cisco IOS XR Software” at the following link: http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.0/routing/configuration/guide/rc3rpl.html#wp1118699.
For further information on Cisco IOS route maps with BGP, consult the document “Cisco IOS BGP Configuration Guide, Release 12.4T” at the following link: http://www.cisco.com/en/US/docs/ios/12_2sr/12_2srb/feature/guide/tbgp_c.html.
Cisco IOS XR BGP process will crash when sending a long length BGP update message
While the long length BGP update message can be caused by any number of attributes, then most common would be the AS Path. Limiting the number of AS numbers in the AS Path Attribute should mitigate this vulnerability. The following shows an example of filtering on AS paths within Cisco IOS XR Software:
route-policy maxas-limit
# Check number of AS Numbers in AS Path attribute.
# If greater than 100 drop the update.
# If less than 100 pass the update.
if as-path length ge 100 then
drop
else
pass
endif
end-policy
router bgp 65533
neighbor 192.168.0.1
remote-as 65534
address-family ipv4 unicast
policy maxas-limit in
policy maxas-limit out
For further information on Cisco IOS XR RPL consult the document “Implementing Routing Policy on Cisco IOS XR Software” at the following link: http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.0/routing/configuration/guide/rc3rpl.html#wp1118699.
Cisco IOS XR BGP process will crash when constructing a BGP update with a large number of AS prepends
There is no workaround for this vulnerability, other than reducing the number of AS path prepends configured within Cisco IOS XR.
I must admit that after reading the document above, a big question sign appeared in my head about the BGP functionality on IOS XR and if we can rely on this in a working environment. I’m sure that Cisco will mitigate this issues as the currently workarounds are just a temporary solution.
A vulnerability exists in the Cisco Firewall Services Module (FWSM) for the Catalyst 6500 Series Switches and Cisco 7600 Series Routers. The vulnerability may cause the FWSM to stop forwarding traffic and may be triggered while processing multiple, crafted ICMP messages.
There are no known instances of intentional exploitation of this vulnerability. However, Cisco has observed data streams that appear to trigger this vulnerability unintentionally.
Cisco has released free software updates that address this vulnerability.
Successful exploitation of the vulnerability may cause the FWSM to stop forwarding traffic between interfaces (transit traffic), and stop processing traffic directed at the FWSM (management traffic). If the FWSM is configured for failover operation, the active FWSM may not fail over to the standby FWSM.
There are no workarounds for this vulnerability. Access control lists (ACLs) that are deployed on the FWSM itself to block through-the-device or to-the-device ICMP messages are not effective to prevent this vulnerability. However, blocking unnecessary ICMP messages on screening devices or on devices in the path to the FWSM will prevent the FWSM from triggering the vulnerability. For example, the following ACL, when deployed on a Cisco IOS device in front of the FWSM, will prevent crafted ICMP messages from reaching the FWSM, and thus protect the FWSM from triggering the vulnerability:
access-list 101 permit icmp any any echo
access-list 101 permit icmp any any echo-reply
access-list 101 permit icmp any any traceroute
access-list 101 permit icmp any any packet-too-big
access-list 101 permit icmp any any time-exceeded
access-list 101 permit icmp any any host-unreachable
access-list 101 permit icmp any any unreachable
access-list 101 deny icmp any any
access-list 101 permit ip any any
The advisory is posted at the following link: http://www.cisco.com/en/US/products/products_security_advisory09186a0080af0d1d.shtml
Some personal observation regarding this vulnerability. I didn’t understood what they mean by “crafted” ICMP packets. In the advisory is posted that “There are no known instances of intentional exploitation of this vulnerability“, then what kind of ICMP packets would kill FWSM? Any usual “ping” (ICMP echo request / echo reply) or it has to be some packet with a special pattern?
If a special pattern is needed then there is a known exploitation of this vulnerability, but due to the fact that Cisco didn’t want any kiddie to try this, they didn’t release the information about what kind of ICMP traffic will foce FWSM to stop forwarding the traffic. In case that any ICMP packet might have an impact for FWSM functionality, then there is a big problem with this hardware.
Also their solution regarding ICMP blocking, cannot be applied in any case. I mean from my point of view as network engineer is OK, but from business impact may be bad, due to the fact that every user or manager use “ping” to check a running service, server or application. Imagine what will happen when 50% of the users will call for support that services are not running :)
UPDATE: Thanks to the comment of João Sena Ribeiro I noticed that the phrase (strikethrough) is a little bit confusing, as I put it in the context that I don’t know what “ping” command will brind down the traffic through FWSM. If there is a known exploit for this (even if Cisco says there is none for the moment), a special pattern can be included also in a simple ICMP echo-request / echo-reply communication, causing the FWSM to hangup. So, if there is no solution for this vulnerability, I would like to block all ICMP traffic, but for the reasons already explained this would not be a good solution.
With its acquisition of wireless LAN design, management and security vendor AirMagnet, Fluke Networks is positioning itself to be a vendor of choice for enterprises that are trying to manage hybridized networks with both wired Ethernet and wireless LAN technology.
“The bottom line is that enterprises are going to have hybrid networks for a really, really long time,” said Paul DeBeasi, senior analyst with Burton Group. “I’m having a lot more phone conversations with enterprises that are looking at new deployments where they want to just go all wireless for network access. What that really means is wireless LAN for access and wired Ethernet used for backhaul and also for switch trunks and data center connections.”