Network technologies and trends:

TCP

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November 9, 2017  3:23 AM

What is “TCP Spurious Retransmission” ? And why does this occur for the FTP traffic passing through a Cisco ASA Firewall?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan
ASA, Cisco, Cisco ASA, Filezilla, firewall, FTP, Network security, TCP

Recently we come across an issue where FTP  connection was not established between the client and the FTP server. The connection was passing through the Cisco ASA Firewall. Upon troubleshooting, we discovered 3-way TCP handshake was happening, however, once the login name and password entered to...

September 30, 2016  11:23 AM

Cisco ASA FirePOWER Services and  High Availability – Series 3

Yasir Irfan Yasir Irfan Profile: Yasir Irfan
Arp, CCIE, Cisco Firewall, Cluster, context, Dynamic Routing, Failover, firewall, HA, LAN, NAT, NetFlow, Routing, Subnets, Syslog, TCP, UDP

The Cisco ASA Firewall with FirePOWER services can be deployed in Active/ Active failover, in this mode the ASAs must operate in multiple context mode.  Cisco is relying on failover groups for active Active/Active failover mode. A failover group comprises of logical groups, of one or more security...


September 26, 2016  4:43 AM

Cisco ASA FirePOWER Services and High Availability – Series 2

Yasir Irfan Yasir Irfan Profile: Yasir Irfan
Arp, Cisco Firewall, Dynamic Routing, Failover, firewall, NAT, NetFlow, Routing, Syslog, TCP, UDP

The Cisco ASA Appliances offers failover in following states

  • Stateless failover
  • Stateful failover.
By default Cisco ASA Appliance performs stateless failover and in this mode of operation, the Active Unit  does the following


September 24, 2016  6:31 PM

Cisco ASA FirePOWER Services and  High Availability – Series 1

Yasir Irfan Yasir Irfan Profile: Yasir Irfan
Arp, Cisco Firewall, Dynamic Routing, Failover, firewall, NAT, Routing, Syslog, TCP, UDP

The Cisco ASA Appliance  with FirePOWER Services is capable of offering high availability using failover and clustering. When it comes to failover , the Cisco ASA supports following types

  • Active/Standby
  • Active/ Active
The Cisco ASA Appliance  with FirePOWER...


November 28, 2015  3:22 PM

Cisco releases VIRL 1.0.0

Yasir Irfan Yasir Irfan Profile: Yasir Irfan
Cisco, Java, Jitter, Latency, link, OpenStack, OpenVPN, TCP

Yesterday I received an email from Cisco VIRL about their new release of VIRL 1.0.0

Hello VIRL Family! Happy Thanksgiving (if you’re celebrating!) We are very happy to announce the release of VIRL 1.0.0 – a major upgrade release packed full of new features! :)
The...


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