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Here's how to set up NordVPN on Cisco router. Get NordVPN@ https://nordvpn.sjv.io/c/376211/570073/7452.

i. Here are some common issues that can arise when configuring and using VPN on a Cisco router:

- VPN tunnel not establishing - Ensure IKE phase 1 and 2 proposals match on both VPN peers. Check access lists, crypto maps, NAT configuration. Verify pre-shared keys match.

- VPN disconnecting intermittently - Could be due to a firewall, NAT, or ACL issue. Enable debugs like debug crypto ipsec, debug crypto isakmp to troubleshoot further.

- Slow VPN speeds - Try changing encryption algorithms in the phase 1 policy to faster ones like AES256 over 3DES. Optimize phase 2 selectors. Verify proper bandwidth allocation.

- VPN traffic not routing correctly - Check ACLs, NAT configuration, routing tables, and crypto maps to ensure VPN subnet routes are allowed and defined properly on each end.

- Client VPN issues - Verify group policy, address assignment, and other client VPN parameter settings match on the server. Reinstall VPN client software if necessary.

- VPN overlapping subnets - Modify VPN subnet ranges to eliminate overlap. Add specific routes to direct traffic properly if subnets must overlap.

- Security association setup issues - Debug IKE negotiation process using show crypto ipsec sa and show crypto isakmp sa commands to isolate P1/P2 errors.

- Cryptomap not activating - Ensure all required ISAKMP and crypto map statements are configured correctly and applied to the proper interfaces.

- Licensing issues - Some Cisco VPN features require specific licensing, so verify the router has the necessary license activated.

- Router resources exhausted - Check CPU, memory and bandwidth usage during VPN setup. Tune VPN crypto algorithms and parameters or upgrade router model if necessary.