The Domain Name System (DNS) provides network-connected nodes with a means of translating hostnames into IP addresses. If a DNS server is not specified for a node, then that node will not be able to use DNS services. If the correct DNS server is not specified, then DNS resolution can take longer than the usual, thus creating the impression that there is a great deal of latency in the network.

If you can ping a site by specifying the IP address, but if the ping fails if you specify the hostname (and ping returns an unknown hostname error or a similar error), then there is a good possibility that the DNS configuration is wrong. If this is the case, you should check the DNS configuration on both the host and the firewall. There is the possibility that the DNS server is down, so you may want to to specify alternate DNS serves. Keep in mind that both Google (8.8.8.8 and 8.8.4.4) and CloudFlare (1.1.1.1 and 1.0.0.1) have their own DNS servers.