Fix 10 common Cisco VPN problems

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Upgrading your NX-OS can be a daunting task as there is always the risk something might go wrong. Saving the configuration can be easily done using the write memory command:. Back to Cisco Firewalls Section. To change, open the client, and, from the options page, uncheck the box next to the stateful firewall option. However, they will give you a place to start as you work on fixing problems with your VPN. Deal with bandwidth spikes Free Download. In the case of the ASA we must use VLAN interfaces, which are configured with their appropriate IP addresses and then next step characterised as inside private or outside public interfaces:.

Detecting and Investigating Unusual Network Traffic


Since the last review, the version has bumped from 7. In fact, its change is significant enough to warrant a full re-evaluation rather than a simple comparison.

For the unfamiliar, Colasoft Capsa Enterprise is a widely respected network protocol analyzer that goes far beyond free packet sniffers like Wireshark. It gives users detailed information about packets , conversations , protocols , and more, while also tying in diagnosis and security tools to assess network health. The installation of Capsa Enterprise is a clear merit, requiring little to no additional configuration.

The installer comes in at 84 MB, a very reasonable size that will be quick to download on most connections. However, Colasoft does give additional options during the process. It lets users remove parts of the network toolset as required to reduce clutter or any other issues. The entire process takes only a few minutes, with Capsa automatically installing the necessary drivers.

Capsa does prompt a restart after completion, though it can be accessed before then to register a serial number. The software offers both an online option for product registration and an offline process that makes use of a license file. After starting Capsa Enterprise for the first time, users are presented with a dashboard that lets them choose a network adapter , select an analysis profile , or load packet files for replay.

Selecting an adapter reveals a graph of network usage over time to make it easier to discern the right one. A table above reveals the speed , number of packets sent , utilization , and IP address to make that process even easier. As data collection begins, Capsa starts to display it in a digestible way, revealing live graphs with global utilization , total traffic , top IP addresses , and top application protocols.

The below screenshot was taken from a packet analyzer and shows an Ethernet frame with the DHCP data payload expanded:. Every field shown in our diagram maps directly to the fields of the captured DHCP packet. While some DHCP servers might not support the Option 82 they are still required to copy the Option 82 value received from the DHCP client and include it in all replies back to the client.

Deal with bandwidth spikes Free Download. Network Analyzer Free Download. Web Vulnerability Scanner Free Download. The user replies with a final ACK packet , completing the process and establishing the TCP connection be established after which data can be transferred between the two hosts: You should be able to notice an uptick in the global utilization graph , as well as the total traffic by bytes: Old NX-OS images might be stable but usually contain a number of bugs and security vulnerabilities that can put your core network and organization in risk.

These additional networks are contactable via a Layer3 device with IP address This is the last step required to successfully provide Internet access to our internal networks. Network Address Translation is essential to masquerade our internal network using the single IP address our Public interface has been configured with.

Network Address Translation, along with all its variations Static, Dynamic etc , is covered in great depth in our popular Network Address Translation section.

We will provide both commands to cover installations with software version up to v8. The following commands apply to ASA appliances with software version up to 8.

Another method of configuring NAT is with the use of access lists. With software version 8. The following commands software version 8. The existence of a DHCP server is necessary in most cases as it helps manage the assignment of IP address to our internal hosts. The Gateway IP address parameter is automatically provided to client and is not required to be configured on the ASA Firewall appliance.

We can verify the DHCP service is working using the show dhcpd statistics command:. Configuring AAA authentication is always a good idea as it instructs the ASA Firewall to use the local user database for the various services it's running.

As mentioned, our example instructs the ASA Firewall to use its local database:. While we always recommend the use of SSH, especially when accessing the Firewall from public IPs, telnet is also an option, however, we must keep in mind that telnet management methods do not provide any security as all data including username, passwords and configurations are sent in clear text.

Telnet does not require any such step as it does not provide any encryption or security:. An essential part of any firewall configure is to define the Internet services our users will have access to. Using Object-groups is easy and recommended as they provide a great deal of flexibility and ease of management. The logic is simple: Create your Object-Groups, insert the protocols and services required, and then reference them in the firewall access -lists.

As a last step, we apply them to the interfaces we need. Now we need to reference our two Object-groups using the firewall access lists. Here we can also define which networks will have access to the services listed in each Object-group: Note that the To understand how Object-groups help simplify access list management: To complete our access list configuration we configure our ASA Firewall to allow ICMP echo packets ping to any destination, and their replies echo-reply:.

Once this step is complete the firewall rules are in effect immediately:. This last step in our ASA Firewall configuration guide will enable logging and debugging so that we can easily trace events and errors.

It is highly recommended to enable logging because it will certainly help troubleshooting the ASA Firewall when problems occur. Issuing the show log command will reveal a number of important logs including any packets that are processed or denied due to access-lists:.

This article serves as an introduction configuration guide for the ASA series Firewall appliances. We covered all necessary commands required to get any ASA Firewall working and servicing network clients, while also explaining in detail all commands used during the configuration process. Back to Cisco Firewalls Section. Deal with bandwidth spikes Free Download.

Network Analyzer Free Download. Web Vulnerability Scanner Free Download. ASA software version 8. This article provides both old style up to v8. ASA config write memory Building configuration We declined the offer and continued with our setup: Security level for "outside" set to 0 by default.