The Cisco ASA supports two types of failover Regular failover Stateful failover Regular failover The instant a failover happens , all active connections are dropped . Clients will need to reestablish connections when the new active device takes over Stateful failover When Stateful Failover is enabled , the active device continually passes per-connection state [...]
Cisco ASA firewall is possibly already configured for multiple security contexts dependent upon how you ordered it from Cisco, but if you are upgrading then you might need to convert from single mode to multiple mode. The context mode (single or multiple) is not stored in the configuration file, even though it does endure reboots. [...]
Basic Guidelines for setting Internet through the Cisco ASA firewall: At first we need to configure the interfaces on the firewall. !— Configure the outside interface. interface GigabitEthernet0/0 nameif outside security-level 0 ip address 10.165.200.226 255.255.255.224 !— Configure the inside interface. interface GigabitEthernet0/1 nameif inside security-level 100 ip address 10.1.1.1 255.255.255.0 The nameif command gives [...]
There are major nat syntax changes after the ASA firewall iOS version 8.3. Regular static NAT: In the pre 8.3- static (inside,outside) 192.168.100.100 10.1.1.6 net mask 255.255.255.255 In the version 8.3 and later- object network obj-10.1.1.6 host 10.1.1.6 nat (inside,outside) static 192.168.100.100 Regular static PAT: In the pre 8.3- static (inside,outside) tcp 192.168.100.100 80 10.1.1.16 [...]
By default tcp idle timeout is 1:0:0 hh:mm:ss. If in case you need to modify it you can do it by MPF (Modular Policy Framework). Let us setup a custom timeout when traffic is coming from particular host 10.77.241.129. !— Match the traffic using the access-list —! object-group service DM_INLINE_TCP_1 tcp port-object eq www port-object [...]
Cisco ASA has very powerful troubleshooting feature in ASA software version 7.2(1) or later that virtually eliminates the guesswork. Packet-tracer allows a firewall admins to inject a virtual packet into the security appliance and track the flow from ingress to egress. Along the way, the packet is evaluated against flow and route lookups, ACLs, protocol [...]
Using packet-tracer it is possible to trace the lifespan of a packet through the security appliance to see if it is behaving as expected. packet-tracer input [src_int] protocol src_addr src_port dest_addr dest_port [detailed] [xml] The packet-tracer command lets you do the following: -Debug all packet drops in production network. -Verify the configuration is working as [...]
Access-Lists Add the ACLs which we will need to NAT, the encryption domain and the group policy. access-list Example_Policy_ACL extended permit tcp object-group Local_LAN object-group Remote_LAN eq 80 access-list Example_Policy_ACL extended deny ip any any access-list Example_VPN_ACL permit ip object-group Local_LAN object-group Remote_LAN Group Policy Create your group policy which will restrict traffic between hosts [...]
The TCP intercept feature is a mechanism to protect the end hosts from TCP SYN-flooding attacks (a type of DoS attack) A SYN-flooding attack occurs when a hacker floods a server with a lots of requests for connection. Because these messages have unreachable return addresses, the connections cannot be established. The resulting volume of unresolved [...]
—-For Site to Site VPN—- Suppose topology is 192.168.10.0/24 inside(ASA1)outside ===VPN=== outside(ASA2)inside 192.168.20.0/24 So on the ASA1 you can configure NAT Exception look like this object network local-obj subnet 192.168.10.0 255.255.255.0 object network remote-obj subnet 192.168.20.0 255.255.255.0 nat (inside,outside) 1 source static local-obj local-obj destination static remote-obj remote-obj —-For Remote VPN—- Suppose topology is 192.168.3.0/24 [...]
1) For Point-to-point VPN Scenario is 192.168.1.x/24 inside(ASA1)outside ===VPN_tunnel===outside(ASA2)inside 192.168.2.0/24 If you were configuring ASA1 nat exemption for this site to site VPN tunnel, it would look like this: object network obj-local-subnet subnet 192.168.1.0 255.255.255.0object network obj-remote-subnet subnet 192.168.2.0 255.255.255.0 nat (inside,outside) 1 source static obj-local-subnet obj-local-subnet destination static obj-remote-subnet obj-remote-subnet 2)For Remote access VPN [...]
Suppose server x is not able to reach server y through the ASA firewall how you will troubleshoot the connectivity?
To check if the access is allowed through the ASA you can use the command packet-tracer packet-tracer input Inside tcp 10.1.1.10 80 (source address/port) 172.16.1.10 80 (Destination addree/port) detailed Packet-tracer will check multiple parameter such as nat,cal,route etc to check if the access is allowed or not. If something is blocking the access it will [...]
What is the transparent mode of Cisco asa firewall? How to change the firewall from router mode to transparent mode?
Traditionally a firewall is a routed hop and acts as a default gateway for hosts that connect to one of its screened subnets. A transparent firewall on the other hand is a Layer 2 firewall that acts like a “stealth firewall” and is not seen as a router hop to connected devices. When the security [...]
ISAKMP can help in negotiation of SAs for security protocols at all the seven layers of the network stack. By centralizing the management of the security associations, ISAKMP reduces the amount of duplicated functionality within each security protocol. ISAKMP can also reduce connection setup time, by negotiating a whole stack of services at once. IPsec, [...]
1.)Cisco TrustSec integration: In this release, the ASA integrates with Cisco TrustSec to provide security group based policy enforcement based on the roles of source and destination devices rather than on network IP addresses. 2.)Cisco Cloud Web Security (ScanSafe): This feature provides content scanning and other malware protection service for web traffic. It can redirect [...]
First set up the hostname on the Firewall using the command hostname hostname sandysasa5510 Generate a key for SSH encryption to use ca generate rsa key 1024 Allow the desired host to connect to ASA/Pix firewall ssh [ip address] [mask] [interface name] ssh 192.168.1.0 255.255.255.0 inside Save cert ca save all Save all your configuration [...]
Yes. Third-party digital certificates which are used in HTTPS (ie. from Entrust, Verisign, Microdoft,etc) that are installed on the Active ASA are replicated to the Standby ASA in an active/standby failover configuration. However, the ASA’s local CA-generated certificates which are used for SSL VPN remote access are not replicated to the standby ASA.
In the older version of Cisco Pix firewalls the serial failover cable on the PIX Firewall is used for failover communication,this cable is limited to six feet. This is the only size serial failover cable that Cisco makes. As such, this is the only length supported. In the latest version firewalls i.e. Cisco ASA firewalls [...]
If a TCP connection has established between two hosts across the Cisco ASA, a TCP RESET-I in the log message means that the server from the inside is sending a reset to the PIX (which instructs the ASA firewall to drop the connection). The ASA then drops the connection and logs a RESET-I. If the [...]
If user has two ISPs terminating on the ASA, the ASA is configured for ISP redundancy. So in some cases users would like to use both ISP to send the traffic outside. In such scenarios the best solution would be to use the Router. Using route-map on the router, one can confgure routing in such [...]
The pre-shared on the Cisco ASA are encrypted to view them in plain text you need to use the command more system:running-config | beg tunnel-group
The traffic we want to be inspected is defined with the use of an access-list. In this example output, the access-list permits all IP traffic from any source to any destination. Therefore, to-be-inspected traffic can be anything that passes through the ASA. ciscoasa(config)#access-list traffic_for_ips permit ip any any ciscoasa(config)#class-map ips_class_map ciscoasa(config-cmap)#match access-list traffic_for_ips ciscoasa(config)#policy-map global_policy [...]
DCD (Dead Connection Detection) detects a dead connection and allows it to expire, without expiring connections that can still handle traffic. You can configure DCD when you want idle, but valid connections to persist. After a TCP connection times out, the ASA sends Dead Connection Detection probes to the end hosts to find out the [...]
Yes it is possible to setup Dead Peer Detection (DPD) on the Cisco VPN client (Cisco software client for connecting to remote VPN gateway). Cisco VPN Client sends its R-U-THERE message to a peer if it has sent traffic to the peer, but hasn’t received response back within ten seconds. This basically means that R-U-THERE [...]
Hair-pinning also called as ‘U-turn ‘.The ASA includes a feature that lets a VPN client send IPSec-protected traffic to another VPN user by allowing such traffic in and out of the same interface using the command ‘same-security-traffic permit intra-interface’ In another application, this feature can redirect incoming VPN traffic back out through the same interface [...]
Unicast Reverse Path Forwarding (uRPF) can be used to help limit malicious traffic on a network. This feature works by enabling a firewall to verify the reachability of the source address in packets being forwarded. This capability can limit the appearance of spoofed addresses on a network. If the source IP address is not valid, [...]
The ASA does the nat in following order 1. NAT exemption (nat 0 access-list)—In order, till the first match. Identity NAT is not included in this category; it is included in the regular static NAT or regular NAT category. 2. Static NAT and Static PAT (regular and policy) (static)—In order, till the first match. Static [...]
The ASA supports a feature that lets a VPN client send IPsec-protected traffic to another VPN user by allowing such traffic in and out of the same interface is called “hairpinning”, this feature can be thought of as VPN spokes (clients) connecting through a VPN hub (Cisco ASA firewall). In another application, this feature can [...]
Unicast Reverse Path Forwarding (Unicast RPF) to help in limit the malicious traffic on an enterprise network. This security feature will work by enabling a router to verify the reachability of the source address in packets being forwarded.This capability can limit the appearance of spoofed addresses on a network. If the source IP address is [...]
Firewall Services Module (FWSM) is a integrated firewall module for Cisco Catalyst 6500 switches and Cisco 7600 Series routers.Up to four FWSMs can be installed in a single chassis, providing scalability to 20 Gbps per chassis. Based on Cisco PIX Firewall technology. Right now FWSM is end of sale & end of life.
We know that the Cisco ASA drops the packets that exceed the MSS value advertised by the client. We can bypass this behaviors by MPF (Modular Policy Framework) ================================================= Cisco-ASA(config)#access-list select_traffic permit tcp any host 192.168.9.2 Cisco-ASA#configure terminal Cisco-ASA(config)#class-map cm_allow_mss Cisco-ASA(config-cmap)#match access-list select_traffic Cisco-ASA(config-cmap)#exit Cisco-ASA(config)#tcp-map mss-map Cisco-ASA(config-tcp-map)#exceed-mss allow Cisco-ASA(config-tcp-map)#exit Cisco-ASA(config)#policy-map pm_allow_mss Cisco-ASA(config-pmap)#class cm_allow_mss Cisco-ASA(config-pmap-c)#set connection [...]
Modular Policy Framework (MPF) configuration defines set of rules for applying firewall features, such as you can use Modular Policy Framework to create a timeout configuration that is specific to a particular TCP application, as opposed to one that applies to all TCP applications Modular Policy Framework features: *QoS input policing *TCP normalization, TCP and [...]
In Asymmetric routing, a packet traverses from a source to a destination in one path and takes a different path when it returns to the source. In Cisco ASA/Pix firewalls, state information is built when the packets flow from a higher security domain to a lower security domain. The firewall will be an exit point [...]
NAT traversal (NAT-T) is a feature that allows IPsec traffic to “traverse” through NAT or PAT points without the incompatibilities that would normally arise. NAT (or PAT) works by translating a local address or addresses to a public address or several public addresses. In the case of PAT, several local addresses are translated to one [...]
In Cisco ASA firewall how to check if it’s under the TCP Syn Flood attack? If it’s under attack what are the counter measures?
In Cisco ASA by running ‘sh connection count’ we can check the number of open connections. By default value for half open connection is 100000 . ciscoasa# show conn count 1931 in use, 3139 most used We can configure the ASA to lower that value by creating class map to select the traffic class-map SYN_Flood_Attack [...]
AAA stands for authentication, authorization and accounting, used to control user’s rights to access network resources and to keep track of the activity of users over a network. The current standard by which devices or applications communicate with an AAA server is the Remote Authentication Dial-In User Service (RADIUS).
ASA uses security levels to determine the parameters of trust given to a network attached to the respective interface. The security level can be configured between 0 to 100 where higher number are more trusted than lower. By default, the ASA allows packets from a higher (trusted) security interface to a lower (untrusted) security interface [...]
SSL VPN provides remote access connectivity from almost any internet enabled location without any special client software at a remote site. You only need a standard web browser and its native SSL encryption. IPsec is a dedicated point-to-point fixed VPN connection where SSL VPNs provides anywhere connectivity without any configuration or special software at remote [...]
Stateful inspection is known as dynamic packet filtering and is a firewall technology that monitors the state of active connections and uses this information to determine which network packets are allowed through the firewall. Stateful inspection analyses packets down to the application layer.
Content Addressable Memory (CAM) Table Overflow Content Addressable Memory (CAM) tables are limited in size. If enough entries are entered into the CAM table before other entries are expired, the CAM table fills up to the point that no new entries can be accepted. Typically, a network intruder floods the switch with a large number [...]