Troubleshooting Slow Browsing

Transcription

1 Troubleshooting Slow Browsing Document Intention This document indents to troubleshoot slow browsing step-by-step. This document is relevant only if Cyberoam is deployed in Route or Bridge mode. Troubleshooting Slow Browsing In case of slow browsing, cross-check the Cyberoam deployment for the following parameters: Denial of Service Settings DNS Resolution Interface Collisions and Errors Multiple Gateways Bandwidth Utilization High CPU Usage Low Disk Space Plain Firewall Rule 1. Denial of Service Settings Reason Either a Denial of Service attack is not detected and dropped or the DoS Settings values are not correctly entered. A DoS attack will cause network congestion which will slow down the network and the slow browsing will just be a side effect. How to crosscheck? I. Press F10 and go to the Dashboard. II. Go to Firewall > Denial of Service > DoS Settings. Check the setting. If it is not enabled, please refer to the Troubleshooting section given below.

2 Troubleshooting Process 1. Go to Firewall > Denial of Service > DoS Settings. Note: Unless specifically advised by Cyberoam Support, do not enable the TCP Flood settings. For optimum results please periodically check the DoS alerts and if any legitimate traffic is dropped, readjust the Packet rate per source and Burst rate per source values. Configure a DoS Bypass rule for a specific IP address if its legitimate traffic is dropped. 2. Press F10 and check the Dashboard. Check the DoS Attack Status section for changes. 2. DNS Resolution Reasons 1. The DNS server is not able to resolve the query. 2. The DNS server is taking to much time to resolve the query 3. In case of Multiple ISP links from different ISPs, if the internal users are using one specific ISP s DNS IP, the DNS traffic may also get load balanced. The requests may travel through different ISP links, ultimately reaching the intended DNS server where as they are originating from other ISP, they will be rejected. The user will refresh if this time the request travels through the right ISP link the query might get resolved. All this will also result in slow browsing. 4. If the LAN users are using an internal DNS server all the requests will first be directed to it and then go to Cyberoam and then to the external DNS server. So the query will take a long time in resolution. Try changing the DNS server to Cyberoam and if the browsing

3 speeds up, please check your DNS server at your end. In case of any further queries, please contact Cyberoam Support. How to crosscheck? Check the DNS Server s Status I. Press F2. Select Diagnostic Tool. II. On the Cyberoam Analytical Tool page check the DNS Server status. In case the DNS Server s status is critical, crosscheck the DNS server. If the DNS Server s status is Ok, then determine the DNS query response time. Refer to the troubleshooting process for more information.

4 In case of Multiple ISP links create a firewall rule to create a static route for the DNS request to pass through the respective link only. Please refer to the screen given below. Troubleshooting process 1. Log in the telnet console of Cyberoam. 2. Select the option 4. Cyberoam Console 3. On the command prompt enter: dnslookup host <website>

5 The Total query time should not exceed approximately 19 msec on the second attempt. 4. If it exceeds the recommended time limit, browse and log into the admin console of Cyberoam. 5. Go to System > Configure > Configure DNS. Follow the steps given in the screen below. 6. Log into Cyberoam s telnet console and recheck the effect at least twice.

6 3. Interface Collisions And Errors Reason 1. Improper link speed or duplex negotiation between Cyberoam and router might result in interface errors and collisions on Cyberoam s WAN port. 2. If the same Subnet IP is bound on multiple interface on Cyberoam. How to Crosscheck I. Press F2. Select Diagnostic Tool. II. Select Interface Info. Troubleshooting process 1. Check and replace the cable. 2. If Cyberoam is directly connected to the ISP router through a Cross Cable, insert a switch between them.

7 4. Multiple Gateways Reason I. The gateways status II. If the gateways are up, there might be connectivity fluctuation III. If there is not connectivity fluctuation, the failover condition might be incorrectly configured. How to Crosscheck There are two ways to check the Gateway Status Press F10 and go to the Cyberoam Dashboard Go to System > Gateway > Manage Gateway(s) Version 9420 onwards Cyberoam sends a mail alert to notify the connectivity fluctuation. If it does not show the red mark, i.e. both the gateways are UP, then please make sure that the failover conditions are set correctly. Refer to the Troubleshooting process. Troubleshooting Process 1. Log into the Telnet console of Cyberoam. 2. Select Cyberoam Console and follow the steps given in the screen below.

8 5. Bandwidth Utilization Reason Check the capacity and the bandwidth utilization of the gateways. If the utilization exceeds the capacity the browsing slows down. How to Crosscheck Check the bandwidth utilization of the gateways System > View Bandwidth Usage. Troubleshooting Process Go to System > Gateway > Manage Gateways. Check the weights of the gateways and divert the traffic to the less utilized gateway. 6. High CPU Usage Reason Slow browsing may occur because of the high load average on the CPU How to Crosscheck I. Press F2 II. Select Diagnostic Tools.

9 III. Select System Health Graphs. IV. Select CPU Info This screen will depict the CPU usage and the peak times. Troubleshooting Process If required, stop the IDP Engine and observe the change.

10 7. Low Disk Space Reason Low disk space may also cause slow browsing. How to Crosscheck I. Press F2 II. Select Diagnostic Tools. III. Check Disk Usage IV. If there is a warning or it is critical status, please follow the troubleshooting process.

11 Troubleshooting process Before you purge the data, please backup the data. Please follow procedure given below. 1. Go to System > Manage Data > Backup Data. Back up your data. To setup Auto-Backup Schedule, please refer to the User Guide. 2. Go to System > Manage Data > Configure Auto Purge utility. Set the schedule to automate purging process. Note: If the Disk Usage problem persists, please contact Cyberoam Support. Once the logs are purged, the data will only be available for view in external viewers.

12 Plain Firewall Rule In spite of all the above mentioned remedies, if the slow browsing complains still persists, then create a Plain Firewall Rule and place it on the top of the firewall rules stack. If this solves the slow browsing complain, please contact Cyberoam Support. What is a Plain Firewall Rule? In a Plain Firewall rule no scanning is enabled and none of the security policies are applied to the traffic passing through Cyberoam. All the parameters that have to be enabled are highlighted screen given below. Document Version: