iPhone

• Unlock your iPhone
• Click on Home button
• Tap on Settings app icon
• Tap on Wi-Fi
• Tap on active Wi-Fi connection. It is a line with blue check mark in it.
• Look for a line with "Router" in it
• IP address of your router is in this line. You can also see your device IP in "IP address" line, DNS server IP in "DNS" line and your network subnet mask in "Subnet mask" line

iPad

• Unlock your iPad
• Click on Home button
• Tap on Settings app icon
• Tap on Wi-Fi
• Tap on active Wi-Fi connection. It is a line with blue check mark in it.
• Look for a line with "Router" in it
• IP address of your router is in this line. You can also see your device IP in "IP address" line, DNS server IP in "DNS" line and your network subnet mask in "Subnet mask" line