Robert, I had similar problem when I tried the same setup using a single NIC per machine for NLB. After I installed another NIC for NLB communication everything cleared out. Configuration was a lot easier and cleaner that way. With a separate NIC for NLB you no longer need Multicast support... Of course that means 3 NICs per box (if you don't have a DMZ), small price in my opinion. John Shepard Network Administrator atinera -----Original Message----- From: Weiss, Robert [mailto:WeissR@xxxxxxxxxx] Sent: Wednesday, November 07, 2001 2:40 PM To: [ISAserver.org Discussion List] Cc: [ISAserver.org Discussion List] Subject: [isalist] RE: ICMP Flood http://www.ISAserver.org John, I should have mentioned that in my post. I am using the Load Balancing on the internal interface only. The IP configuration for my server is as follows: External Interface IP Address 207.254.161.xxx/27 Default Gateway 207.254.161.yyy - Router Internal Interface IP Address 172.24.1.160/16 172.24.1.158/16 - Cluster Address Default Gateway Not set as per Microsoft documentation Robert Weiss Manager, Network and Academic Systems Philadelphia University Office of Information Technology 215-951-2689 http://www.PhilaU.edu/OIT <http://www.PhilaU.edu/OIT> -----Original Message----- From: John C. Shepard [ mailto:jshepard@xxxxxxxxxxx <mailto:jshepard@xxxxxxxxxxx> ] Sent: Wednesday, November 07, 2001 5:34 PM To: [ISAserver.org Discussion List]; weissr@xxxxxxxxxx Subject: RE: ICMP Flood Robert, are you Load Balancing the internal interface? John Shepard Network Administrator atinera -----Original Message----- From: Weiss, Robert [ mailto:WeissR@xxxxxxxxxx <mailto:WeissR@xxxxxxxxxx> ] Sent: Wednesday, November 07, 2001 2:29 PM To: [ISAserver.org Discussion List] Subject: ICMP Flood Importance: High We are having a strange problem with our ISA Servers. We currently have three stand-alone servers running in integrated mode using Network Load Balancing to create an ISA "cluster". When ever we try to add a fourth server to the cluster, our network is overrun with ICMP floods. What I see when I "sniff" my network is thousands of "Destination Host Unreachable" packets with the IP address of my DNS/WINS/DHCP Servers to the IP address of my ISA Servers. If I can't get Network Load Balancing to work, we will need to go back to Round Robin DNS, unless someone else has a good load balancing solution. Please reply directly back to weissr@xxxxxxxxxx < mailto:weissr@xxxxxxxxxx <mailto:weissr@xxxxxxxxxx> > as well as posting to the list if possible. Thank you, Robert Weiss Manager, Network and Academic Systems Philadelphia University Office of Information Technology 215-951-2689 http://www.PhilaU.edu/OIT <http://www.PhilaU.edu/OIT> ------------------------------------------------------ You are currently subscribed to this ISAserver.org Discussion List as: john@xxxxxxxxxxxxxx To unsubscribe send a blank email to $subst('Email.Unsub')